Thinking about the things I've accomplished and gained through the years help me raise my feeling of self-esteem or self-worth. For others, if I know them well enough, then I do the same for them. I can list the good things I think they've done, and it usually does the job.
I think it's admirable to be lifting one's friends up, helping them be the best they can be and the benefits flow on to oneself as you have described.