“Desire is the brain’s strategy for action. As we’ve seen, it can be both a threat to self-control and a source of willpower. When dopamine points us to temptation, we must distinguish wanting from happiness. But we can also recruit dopamine and the promise of reward to motivate ourselves and others. In the end, desire is neither good nor bad—what matters is where we let it point us, and whether we have the wisdom to know when to follow.”