The biggest mistake you can make is to not learn from your mistakes.
You're gonna mess up. You're young, you're human, you're awkward. It's ok.
What's important is that when you make a mistake, you learn from it and you make up for it.
There are tons of mistakes that can get you fired - Tweeting or Facebooking, sharing proprietary information, emailing the wrong person the wrong thing and the list goes on.
But let's say you did something small enough to get your boss's feathers ruffled but not big enough to get you fired, what now?
Here's a quick to do list:
1. Do not cry. In public at least.
2. Acknowledge your mistake.
3. Apologise + accept blame.
4. Ask what you did wrong and how to not do it again.
5. Overachieve.
6. Never ever ever do it again. Ever.