If you can find younger training partners, make an effort to run with them regularly. Being around runners who are still chasing PRs is a wonderful antidote to getting bogged down in a woe-isme-I’m-so-old-and-slow self-pity party. You can feed off of their enthusiasm, and you can put your hard-earned wisdom to use in mentoring them. Several friends of mine have found their running reborn by coaching and running with high schoolers.