Mana

Willpower is a fungible depletable resource. If we use willpower on one thing, we don't have it for a later thing until we replenish our store of willpower.

Willpower is key to our success in life.

But calling it willpower makes it easy to understand that it is like calories, something we need to replenish and something that we burn.

We need a new word. I propose: Mana.