When I turned sixty (60) I started taking short cuts on group rides to keep contact with the younger riders. It kind of made me lose some of the impetus to train hard. I have since (seven years later) moved to the old folks state of Florida. Now I am more motivated than ever to train hard because there are lots of people my age here who stay fit and competitve.
Don't stop being competitive. Performance is quite relative to who you are up against. Find a group of riders your age, and enjoy.....you'll feel much better.