The answer, surprisingly, is not that they have more will or discipline than you do. The counterintuitive secret to getting things done is to make them more automatic, so they require less energy.
It turns out we each have one reservoir of will and discipline, and it gets progressively depleted by any act of conscious self-regulation. In other words, if you spend energy trying toresist a fragrant chocolate chip cookie, you’ll have less energy left over to solve a difficult problem. Will and discipline decline inexorably as the day wears on.