Daniel Goleman - Author of Emotional Intelligence and Social Intelligence

Those of us who struggle to resist junk foods or otherwise suffer a lack of will power will be heartened by some good and bad news from neuroscience.

First, the bad news.  A slew of studies suggest that we each have a fixed neural reservoir of will power, and that if we use it on one thing, we have less for others.  Tasks that demand some self-control make it harder for us to do the next thing that takes will power.  In a typical experiment on this effect, people who first had to circle every ‘e’ in a long passage gave up sooner when they then had to watch a video of a fixed, boring, scene. The same loss of persistence has been found when people resist tempting foods, suppress emotional reactions, even make the effort to try to impress someone.

This all suggests we have a fixed will power budget, one we should be careful in spending. Some neuroscientists suspect that self-control consumes blood sugar, which takes a while to build up again, and so the depletion effect.

But the good news is that we can grow our will power; like a muscle, over time the more we use it, the more it gradually increases. But doing this takes, of all things, will power.