In each case, you would have relied on your willpower, which psychologists define as the ability to avoid short-term temptations and override unwanted thoughts, feelings or impulses. And some people seem to have much greater reserves of it than others: they find it easier to control their emotions, avoid procrastination and stick to their goals, without ever seeming to lose their iron grip on their behaviour. Indeed, you may know some lucky people who, after a hard day at work, have the resolve to do something productive like a workout – while you give up on your fitness goals and fall for the temptations of junk food and trash TV.