Like you, I was experiencing guilt and shame to where it controlled my mood and day to day living. I've been reading self-help books and one of them said that we all have scars or things we wish we would have never said or done, but the key is forgiveness of youself. Hey, we're only human and everyone makes mistakes. If you can put your finger on it and know what you're ashamed of you can ask yourself is it something I can apologize for? If it's too hard to talk about, how long are you going to let yourself suffer? Set a time limit and let it go, it's the past and we all can learn from our mistakes. Try to forgive yourself because I'm sure we would forgive someone for something they were ashamed about.