What stage of endurance sport are you experiencing? Fully engaged, or barely hanging on to the identity? It does seem to ebb and tide over the years. Heard a great podcast on Dirt Dawg's Running Diatribe, where he discussed "Running on E", where E = emotion. That's what has driven him over the past 20+ years, channeling emotion into the effort.
Can you think of another athlete who has done well with "Running on E?" I'd call out Lance Armstrong, who had a rough childhood with numerous step-dads. Lance many times dealt with the "E" of anger and pushed it through his body to top performances.
I emailed Mike (aka Dirt Dawg) and expressed my support for his "E" plan. Let him know that my 28 years in the sport have been based on "Running on R"....for random. I enjoy NOT having plan, letting things unfold each morning as I head to the gym or out for a jog. No real goals or models to follow. Just let it happen. Bike rides on weekends and evenings (in summer months) are fairly regular, but the intensity and effort aren't. Some days I spin hard and run with the lead pack, on other days I melt off the back and am fine with it.
What letter represents the basis for your longevity in endurance sport? It's fun to examine the essence of our being.