I actually have been contacting some people from my past that helped me and either never knew it, or I had lost touch with them and needed to track them down to tell them how much they made a difference in my life.
For example. I had a third grade teacher who always held hands with kids at recess. I sent her a little card, thanking her for that because I have fond memories of her warm mittens.

But I also told her that what she didn't know was that my house was an abusive nightmare and holding her hand in the schoolyard gave me a dose of human kindness that I wasn't getting anywhere else. It gave me hope.
She was very appreciative. She had just lost her mother and was feeling very down and out when she got my card.
I'm contacting people like that. So, the tracking down and investigating their whereabouts gets me out of my own head for awhile, and I don't have to think "I should've told that person what that one kind gesture meant to me" because I am actually doing it.