I got written up at work last week.
Why did you get written up at work?
I could not handle pressure and I messed up at work
It sounds like you broke a rule if you were written up. It is bad to break rules at work.
It was a mistake. I should have not been written up and this is a sign that they don't appreciate my work.
It sounds like you made a mistake and have learned from it. Don't you think you will be more careful next time so that you don't make the same mistake again?