I’ll go with an abstract suggestion because reading stories about over people’s athletics triumphs does nothing for me. Try “An Anthropologist on Mars” by Oliver Sacks. Oliver Sacks is a clinical psychologist - he wrote the book that inspired the movie Awakenings (with Robert DeNiro) - This book highlights seven case studies with people with unique disorders/conditions, but he treats them as attributes, not handicaps.
But when I need to dig deep in a race, I’m not thinking about Prefontaine’s 5k finish, I’m thinking of the expression on my daughter’s face at the finish line, or what it will be like telling my boss I dnf’d. My advise is stock yourself up with a myriad of those mental queues and trigger them as necessary. I like to box myself into a corner this way, maybe talk some smack at work so you have to live up to it. Tie in your goal with a charity, so when it get’s rough you know you have to “do it for the children”.
I just had a rough time at Arizona 70.3 and needed to use every mental angle possible to will myself to finish and in the end the thing that did it was I realized I do this for fun and I decided to stop beating myself up about time goals and just enjoy the race. Then I noticed how beautiful the sky was, how amazing the crowd support was, how nice the other racers where, how delicious Honey Stinger Fruit Smoothie gels are.
neurologist.