Don't stress over it - nobody's firing you. As long as you're putting in the long hours and not making mistakes that's costing the firm huge money, they'll keep you because that's all that's expected of you as an A0.
Here are a few tips that might help since I was an A0 not many years (an SA now):
1. When you're working long hours, you have the absolute right to take sufficient breaks. Don't hesitate to go out for a walk/jog in the evening because you think you may get a call from your seniors - nobody's dying if you don't respond within 30 minutes but you will if you don't take of yourself.
2. If people haven't specifically told you there's work on weekend, it's yours. Don't waste it anticipating that there might be work.
3. Even if there's work on weekends, you're entitled to a few hours to yourself. You can assertively tell people that you have a lunch, you're going out and will come back and do whatever work is required. Most seniors give you work on weekends because they have nothing else to do. Your life does not need to sync theirs.
4. When you're going out, stop carrying your laptop around. If you're on leave or a weekend, it's completely okay to be away from your system or not have access to internet.
5. Learn to enjoy the little breaks you get between work - if you're waiting for someone to call back or email you the document back with comments and edits, then watch a YouTube video, go make some tea/coffee (buy some fancy tea/coffee brands if they make you feel good), call up your friend or do some exercise.
6. While people at law firms appear serious and cranky (I imagine I do too to my juniors), remember most of them are also people like you. They have similar stories, problems, anxieties and aspirations like you. They also want to go out without the anxiety that partner might call any moment. So, try talking frankly with them as a friend who's in the same boat as you. Something like, "Hey, if you have some plans on Saturday, let me know and I'll take over the work. I'll need a few hours off on a Sunday." If a junior told me that, I'll do whatever I have to ensure his/her Sunday is free. Truly having each others back makes life ten times easier for everyone.
So, yes. Just hang in there a little more. I won't tell you it gets better - but I can tell you it gets much more bearable with time as you learn the tips and tricks. And none of us really want to do this forever. We all have our exits and entrances - just play your part for the time that you are here and enjoy the show.
I am very sorry to hear about what has happened to you. While there could have been some diligence exercised on your part (in the incident described in the first paragraph), it is not a major fault at all. A firm which wants people to leave for such incidents is not a place worth working at. Despite the deadline not being close enough, it is upto the seniors to review the work you have done, and point out shortcomings, if any, politely, and tell you how to go about things in the correct manner. Quite clearly, the SA and PA have failed in their duty here.
Coming to the Second Paragraph, assuming you were on time everyday and were decent at your work, and you were late on only this one occasion (assuming there was no urgent deadline / meeting on the day you were late), again, the way the partner went about the entire thing seems very unreasonable and unprofessional. The partner asking you to leave merely on the basis of others' review is pathetic on his/her part - looks like he/she forgot the very basic legal principle of "Audi Alteram Partem" - Hear the Other Side (assuming he/she did not hear you out and asked you for your side of the story).
This doesn't sound like underperformance to me, as I have heard several stories like these. It looks like the firm was hell bent on cost cutting, and they need to blame someone for the same and send them out. No firm is ever going to reveal that they have a cost crunch issue or not enough work. For now, I can only say that be patient, be thorough with the work you have done, only put out on your CV the work that you are confident talking about, and keep applying continuously to other places. Get in touch with legal recruiters as well. Something will definitely work out, even if it takes time.
It is supremely unlikely that an A0 will get fired. You need to mess up really, really, really bad before someone even considers firing you. If you do not have a lot of work, or made a lot of mistakes, they might extend your probation, but they will rarely fire someone for either reason, especially an A0. Some smaller firms might let you go for budgetary reasons, but it's rare at the big ones (other than some teams, according to rumors).
As for 1.1, I really think joining a new firm and working from home is much worse than working from the office (not saying that offices should re-open). Weekends and late-hours were a bit rarer. This is mostly because even cranky partners would usually just ask you to do something the next day. These days everything is EOD or first thing in the morning. People just assume that because you are at home, you have more time (you actually have less time at home, my utilization is consistently at least 10-20% higher than WFO). People were also a lot nicer in person, because it's difficult to yell at someone or wake someone up at 3AM if you need to see them in the morning.
A piece of advise would be to stand your ground. Don't give short timelines when asked (if you need 8 hours, say 12), notify your seniors if deadlines are not manageable, speak to seniors about stuff other than work (so they remember you as more than a glorified intern). It's okay to say no to more work if you already have 12-15 hours of work a day. These things won't lead to you being fired. If some partner throws a fit and complains about 'bandwidth issues', leave in a year or two and go to a better place. I did that and I'm a lot happier.
Remember that despite what you read from the trolls here, there are a LOT of vacancies at all firms constantly. There are teams and firms that have not been able to fill those vacancies despite the trolls insisting that there are 'hundreds of applicants'. I've received multiple pitches for one of these 'bigger platforms' despite switching only a few months ago. You are not as replaceable as they want you to think (especially once you get through the first year or two).
Here are a few tips that might help since I was an A0 not many years (an SA now):
1. When you're working long hours, you have the absolute right to take sufficient breaks. Don't hesitate to go out for a walk/jog in the evening because you think you may get a call from your seniors - nobody's dying if you don't respond within 30 minutes but you will if you don't take of yourself.
2. If people haven't specifically told you there's work on weekend, it's yours. Don't waste it anticipating that there might be work.
3. Even if there's work on weekends, you're entitled to a few hours to yourself. You can assertively tell people that you have a lunch, you're going out and will come back and do whatever work is required. Most seniors give you work on weekends because they have nothing else to do. Your life does not need to sync theirs.
4. When you're going out, stop carrying your laptop around. If you're on leave or a weekend, it's completely okay to be away from your system or not have access to internet.
5. Learn to enjoy the little breaks you get between work - if you're waiting for someone to call back or email you the document back with comments and edits, then watch a YouTube video, go make some tea/coffee (buy some fancy tea/coffee brands if they make you feel good), call up your friend or do some exercise.
6. While people at law firms appear serious and cranky (I imagine I do too to my juniors), remember most of them are also people like you. They have similar stories, problems, anxieties and aspirations like you. They also want to go out without the anxiety that partner might call any moment. So, try talking frankly with them as a friend who's in the same boat as you. Something like, "Hey, if you have some plans on Saturday, let me know and I'll take over the work. I'll need a few hours off on a Sunday." If a junior told me that, I'll do whatever I have to ensure his/her Sunday is free. Truly having each others back makes life ten times easier for everyone.
So, yes. Just hang in there a little more. I won't tell you it gets better - but I can tell you it gets much more bearable with time as you learn the tips and tricks. And none of us really want to do this forever. We all have our exits and entrances - just play your part for the time that you are here and enjoy the show.
Coming to the Second Paragraph, assuming you were on time everyday and were decent at your work, and you were late on only this one occasion (assuming there was no urgent deadline / meeting on the day you were late), again, the way the partner went about the entire thing seems very unreasonable and unprofessional. The partner asking you to leave merely on the basis of others' review is pathetic on his/her part - looks like he/she forgot the very basic legal principle of "Audi Alteram Partem" - Hear the Other Side (assuming he/she did not hear you out and asked you for your side of the story).
This doesn't sound like underperformance to me, as I have heard several stories like these. It looks like the firm was hell bent on cost cutting, and they need to blame someone for the same and send them out. No firm is ever going to reveal that they have a cost crunch issue or not enough work. For now, I can only say that be patient, be thorough with the work you have done, only put out on your CV the work that you are confident talking about, and keep applying continuously to other places. Get in touch with legal recruiters as well. Something will definitely work out, even if it takes time.
As for 1.1, I really think joining a new firm and working from home is much worse than working from the office (not saying that offices should re-open). Weekends and late-hours were a bit rarer. This is mostly because even cranky partners would usually just ask you to do something the next day. These days everything is EOD or first thing in the morning. People just assume that because you are at home, you have more time (you actually have less time at home, my utilization is consistently at least 10-20% higher than WFO). People were also a lot nicer in person, because it's difficult to yell at someone or wake someone up at 3AM if you need to see them in the morning.
A piece of advise would be to stand your ground. Don't give short timelines when asked (if you need 8 hours, say 12), notify your seniors if deadlines are not manageable, speak to seniors about stuff other than work (so they remember you as more than a glorified intern). It's okay to say no to more work if you already have 12-15 hours of work a day. These things won't lead to you being fired. If some partner throws a fit and complains about 'bandwidth issues', leave in a year or two and go to a better place. I did that and I'm a lot happier.
Remember that despite what you read from the trolls here, there are a LOT of vacancies at all firms constantly. There are teams and firms that have not been able to fill those vacancies despite the trolls insisting that there are 'hundreds of applicants'. I've received multiple pitches for one of these 'bigger platforms' despite switching only a few months ago. You are not as replaceable as they want you to think (especially once you get through the first year or two).