Rules you set for yourself only count if you’d follow them on a bad day.

A rule that works when you are rested and in a good mood is not a rule; it is a preference. The point of setting one is to decide now, while you are thinking clearly, what you will do later when you are not. If it cannot survive a bad Tuesday, it will not be there on the day you need it.

Take a rule you keep loosely and shrink it until you would do it tired: ten minutes of study, not two hours. Decide in advance what the bad-day version looks like. A small rule kept intact beats a large one broken twice a week.