I hate christmas because it reminds me of something bad I've done
What's the bad thing you did?
It was a situation on christmas. I don't want to talk about it.
If you have something in the past that is bothering you that much then you should go to therapy for it. Therapy might be able to help you start to move on over your past trauma.
Nah, I'm not doing that. I'll just deal with it on my own.
But if it's bothering this much, you should talk to someone. How about a friend or family, specifically someone who experienced this bad time with you?