Some neuroscientists go so far as to say that we have one brain but two minds — or even, two people living inside our mind. There’s the version of us that acts on impulse and seeks immediate gratification, and the version of us that controls our impulses and delays gratification to protect our long-term goals. They’re both us, but we switch back and forth between these two selves. Sometimes we identify with the person who wants to lose weight, and sometimes we identify with the person who just wants the cookie. This is what defines a willpower challenge: Part of you wants one thing, and another part of you wants something else. Or your present self wants one thing, but your future self would be better off if you did something else. When these two selves disagree, one version of us has to override the other. The part of you that wants to give in isn’t bad — it simply has a different point of view about what matters most.
— The Willpower Instinct (Kelly McGonigal), Loc. 303–9