Man, you're a bit of a roller coaster eh? Up & down, Up & and down. The trick is to not get too attached to temporary feelings. Feelings, whether good or bad, are temporary of course, but they can also be pretty powerful which causes us to attach ourselves too them. Realizing that how you feel now has absolutely nothing to do with how you will feel tomorrow is key. When you feel bad or depressed, and you don't accept it as it is, you will feel another layer of guilt on top of if all, which can make returning to a positive state take longer than it should. When you feel really good, you attach yourself to that feeling and begin to make it into a 'sense of self', which sets you up for a huge crash when you're having a low day(which is inevitable).
Take feelings as they are without attachment, and you will find peace.