I find that whenever I ruminate about a sad event in my personal history, or a string of events such as relationship failures, it's because I'm looking for confirmation that I'm hopeless and doomed to never experience success in, e.g., my relationships with others. Truth be told, it isn't really me. It's Depression talking. She's an evil b**** that sits on your shoulder and whispers terrible things in your ear whenever you start to feel hopeful about life. It's her job to bring you as low as she can. Your job is to fight her to the best of your abilities and try to take away her purpose for existence.

CBT skills would be extremely helpful here. Do you have Cognitive Behavioral Therapy experience?