Apparently seeing other people exhibit self control or even just thinking of them tends to increase (or decrease if observing poor self control) one's own self control.
Also the inverse seems to be true: watching someone fail to exert self control makes it more difficult for you to. My husband's laziness has proven dangerously contagious.
Just saw this article on reddit and thought it would be relevant here: Self Control is Contagious, Study Finds
Apparently seeing other people exhibit self control or even just thinking of them tends to increase (or decrease if observing poor self control) one's own self control.