If your reason only works when you’re in a good mood, go find a sturdier reason.

Motivation that depends on feeling good is a fair-weather arrangement, and the days you most need a reason are the days you feel worst. A sturdy reason does not have to be inspiring, and usually is not. It tends to be something plain that stays true while you are tired, such as an obligation to a person, or a fact about what you want that does not move with your energy.

Write in one line why you are doing this, then test it against a bad Tuesday. If it does not survive, keep looking until one does.