And no, I don’t mean self-indulgence. That’s making something that you crave. Wanting is the inner voice that you want to call “you” that tells you “wake up early” or “finish that project” or “ask her out”; craving is who you blame after regret is part of your present.
Willpower is your skill to bring your true self into this world.
And it’s ok if you’re weak—as long as you do something about it.
Regarding how, I’ve found is the same as with physical power: train, eat, and sleep; there’s no shortcuts.