The power for self-discipline does not come from admiring self-discipline. It does not come from wishing we were more self-disciplined. It does not come from making new resolves, plans and schedules for self-discipline (though these help when the fundamental motivation is right). It certainly does not come from loathing our lack of self-discipline and resolving (again) to do better — and this time we mean it. The power for self-discipline comes from the prize — whatever we really want, the reward we believe will yield us the greatest pleasure.

https://www.desiringgod.org/articles/the-secret-to-self-discipline