Lack of self discipline makes smart people do stupid things. It's familiar to hear of people who are unable to kick bad habits even where the benefits are self evident. For example, doctors are all too familiar with people failing to change their diet or lifestyle even after they have been warned that continuing as they are will result in a certain early death.
Lack of self discipline also makes becoming a better thinker harder. Solving tough mental problems requires dedicated practice, and staying on the task. And ultimately there's not much point in becoming a better thinker if you don't put that thinking into practice, and still do dumb things by acting on impulse rather than reason.
So this page is here to explore ways of improving self discipline.
As a starting point this article in the New York Times suggests that self discipline is a skill which can be learned and exercised.