Adaptation comes through challenge.
This is no big secret.
The question is, what adaptation and what's the minimum challenge I can use to get that adaptation.
The adaptations we train for are the various attributes we need in order to best perform.
That's up to you. For some it's a full contact martial art, for others it's playing with their kids. Whatever it is, it's your reason.
But the key is always to train in order to improve your performance. The training should never become the performance.
Train to adapt. Train to develop attributes.
Occasionally test these attributes through performance
But don't mistake training FOR performance