Musashi's transfer
The Book of Five Rings claims mastery of one way teaches all ways: the attention, patience and honesty required transfer to everything else a man does.
Habit is the mechanism
Aristotle supplies the engine — repeated right action becomes character — and Rippetoe supplies the physical proof in progressive load.
Choose and stay
Pick one craft for the next five years. Depth is the rare thing; dabbling is abundant and cheap.