Kelly McGonigal defines willpower as "the ability to do what you really want to do when part of you really doesn’t want to do it." It consists of three competing elements: 1) I will – the ability to do what you need to do; 2) I won’t – the other side of self-control; the inability to resist temptation; and 3) I want – your true want, the ability to remember the big picture of your life. Often when we castigate ourselves for impulsive actions, we  say we weren’t “thinking”. I interpret that as saying we weren’t considering the Big Picture. We were operating on a concrete level, not thinking beyond the moment.

Reference: McGonigal, K. (2012). The willpower instinct: How self-control works, why it matters and what you can do to get more of it. New York: Avery.