I ate ham and liked it and have some guilt about it.
Why are you feeling guilty?
I promised myself and my friends I'd stay vegan, but now I broke that promise.
It seems you feel that you should not be eating ham. However, if this is something that you enjoy, you should not punish yourself for eating it. Eating foods that you enjoy is a part of being yourself and you should feel comfortable with who you are if you know that you aren't doing something wrong.
Don't tell me what to do.
That's fine, if you want to eat ham, eat ham.