I also write but I think in a slightly different way. It took a lot of doing but I convinced myself that when things get on top of me I should just write my thoughts in something similar to a diary, though it's a diary I never intend to look back on if I feel I couldn't face what happened or my thoughts of the past, which are sometimes, as you described, trash.

If one day I feel I can look back and be fine, I might, though I'd be just as content binning the book and never looking back. The past is the past, if I can look back and learn, that's fine. If I need to leave it behind then perhaps leaving the past behind is the lesson.