I cheated. It still hurts.

I messed up bad, years ago. I was with Mark, and I cheated on him with his best friend, Dave. It only happened once, a drunken night after a party. I felt so guilty, I ended things with Mark a few weeks later, but I never told him the real reason. I just said I wasn't ready for a serious relationship. He was heartbroken. Dave and I never spoke about it again, and now they don't talk anymore. I still see Mark sometimes, and he's doing okay, but every time I see him, the guilt eats me up. I wish I could tell him the truth, but I'm afraid of ruining everything, again. Maybe it's better if I just keep quiet, but God, it's heavy.