Jordan, first and foremost, take a day or two to let yourself grieve a bit if you really wanted that job. No matter what anyone says, it hurts when you put in significant effort trying to succeed and for whatever reason does not work out. Just get it out of your system, eat like a fatass for a day, drink a beer or two, eat pizza, throw something at the wall, yell things out loud like “I never liked your firm anyway!”, and just let it all out. It sucks to fail.
Second, you are not alone. This happens to tons of people every busy season – interns, staff, people who can't pass the cpa exam, etc. Public accounting is brutal. I'm an Army Veteran and went through two busy seasons as an intern in public. I'm also likely significantly older than you. It was really difficult for me. I usually get along well with everyone. I'm a manager's dream – I show up every day, earlier than most, I come in no matter what is going on in my personal life, I ask for feedback, am constantly trying ways to work more efficiently, and usually end up being a trainer because I pay so much attention to detail.
All that considered, my public accounting experiences were terrible. The hierarchy in public accounting is strange and difficult to adjust to. You don't have a boss really. You have 15 bosses. So you don't really have anyone you can lean on when you don't understand. They bark at you, then walk away. What I found was the reason for my failure and the reason other people succeed is that the successful people were able to connect with mentors or other peers who could considerably help them. I was about fifteen years older than everyone in both circumstances and felt alienated and excluded for that very reason. I tried warming up to anyone really and it just never happened. And I'm someone who is friendly and usually can connect with a lot of people at work.
Third, everyone makes errors in tax. It's how you learn. Everyone does it and some partners, managers, and sometimes seniors shit all over their staff at every turn because they've never worked outside of public accounting and have terrible leadership/personal skills. I can honestly say I've never been spoken to the way I was in both firms over what was arguably pretty reasonable mistakes for new staff. I had people insult me personally, take me into their office multiple times (which has never happened to me in my entire professional career prior to starting in public), and overall just get barraged with nothing but negative feedback. I heard a single positive thing from a single partner in two busy seasons. And keep in mind, I am a VERY dedicated employee. I devoted extra time learning everything I could. I adjusted when they made suggestions, stayed late, had almost 100% utilized billing hours, etc. I also made excellent grades, am active at my university, etc. I'm not a slouch by any means.
And finally fourth, there are a billion great opportunities to excel in accounting outside of the public accounting grind. Don't beat yourself up too much. A strong work ethic is one of the greatest assets you can possess. Especially in modern times where so many people wants more than what they're worth but don't want to put in the hours. People admire old fashioned character – 1) Resilience, 2) Perseverance, 3) Diligence, 4) Confidence (not feigned confidence in the form of arrogance), 5) Dedication, etc. You can find employers everywhere looking for someone who has these characteristics combined with the well-respected CPA license. Don't believe the hype that public is all there is. I personally found public to be more about who you are, who you know, and what you have, more than specifically what you're capable of. There's some elements of elitism in certain firms and you've already been ruled out before you walk in the door. It's life, man. It sucks, but it's real.
Good luck!