Derek doesn't tell anyone the real reason for his neverending workouts and runs in the woods, for the way he keeps pushing himself harder and trains more and more, beyond what he expects from the Betas.

When he runs, when he moves, when he's on the hundredth pull up, that's when his muscles finally start aching and pulling, when he feels... when he feels.

He almost forgot how to - he stopped that day when Laura packed up whatever they had left and he wordlessly sat by her side on their drive across the country - and while forgetting the pain seems like a good thing, he's not going to let himself do that again.