After 50 years of agonizing over why I failed academically, I realized the problem was my "inability to organize and to sustain a directed effort". So I would tell myself: 1) to explicitly work on organizing my efforts as opposed to relying on my ad hoc approach; 2) to develop formal routines intended to help me sustain my efforts by frequently renewing my commitment to those efforts; and 3) to work on formally defining my goals rather than working from hazy intuition.
Also, I would tell myself to work my butt off during the week and kick back on the weekend.