Willpower is what you use when you’re allowed choice and know you should make the good choice but actually feel like choosing the bad choice. The trick to good discipline is to never allow it to be a choice. There are no excuses. There is no negotiation. It just is the same way the sun rises or the tax man comes. Good discipline is a skill you develop and it is far easier than trying to live via something as temperamental as willpower.

You need some level of willpower to get your legs to take you to another place. Certainly if it involves getting in a car and parking.

If you don't have that, the skill needed to develop it is the skill to get someone to prescribe you amphetamines.