Great advice. I've done ultra marathons, powerlifting and strongman (open division). Knowing I'll never be the best and there is an upper limit I've created my own goal Project 15-50. Complete the big three lifts (squat, bench and deadlift) for a total of 1500lbs and run a 50 miler within a week, a three year goal.
Though I do feel I need to see what my mind can accomplish. I'm a DS Manager (was an air traffic controller) but the role isn't technically difficult.
I find that personally this is a big one for me, except I spend my time road cycling. Depending on who you are the competitive aspect of group riding can be very enjoyable. (Different sports may be a better fit depending on who you are)
see what your body can do, it is clear that your mind has accomplished a lot
the contentment of a great workout is hard to beat