You're old, and getting older. Is thinking and obsessing what you want, or to do something that stops your regrets from this moment on? In space we can move backward and in all directions, but in time all that we're given is moving forward. Think about that. Time doesn't stop if we stop living our lives. It's a moving train, even if we're sitting.

Talk to your neighbor, get close to him/her. If you cannot do anything about your own thinking and obsession, seek therapy. Just talking with your "paid friend" is better than keeping yourself in the cycle. In my experience, when I'm depressed or angry about something, just talking about it to someone changes my mood.

Good luck