When we’re on our best behavior, humans’ ability to control our impulses puts other species to shame. But all too often, we use our fancy brains not to make the most strategic decisions, but to give ourselves permission to act more irrationally. That’s because a big prefrontal cortex is good at more than self-control. It can also rationalize bad decisions and promise we’ll be better tomorrow. You can bet those chimpanzees weren’t telling themselves, “I’ll take the two grapes now, because I can always wait for the six grapes next time.” But we humans have all sorts of mental tricks for convincing ourselves that the time to resist temptation is tomorrow — and so we of the gigantic prefrontal cortices find ourselves giving in again and again to immediate gratification.
— The Willpower Instinct (Kelly McGonigal), Loc. 2388–93