On the other hand, self-control is what makes the civilized world civil. What makes for self-control? In the abstract it is enlightened self-interest. In the short term, it can be your brain chemistry.
It turns out that weakness in your body can reduce your self-control, and cause you to over-eat, drink too much, lash out at someone, and so on. This can be caused by being hungry or tired, or intoxicated.
Another factor is mental tiredness or preoccupation with some pressing problem. Let's say you got a ticket on the way home from work, and then when you get home you kick the dog. One day I thought I lost my glasses, and I was rude to a guy at work. This is odd, since I usually am polite and politically correct. I was worried about getting my glasses back, and was unable to process the right response in this social situation.
Self-control has a limit too. People think of it as a muscle. If you skip a donut and go exercise, you may reward yourself with something later. I good antidote to that is routine. If you never eat donuts and always exercise, then practicing your routine takes little willpower. Being out of your routine, creates temptation and a little higher stress level, and that can lead to failure.
A good article on this is by Maia Szalavitz at Time.
