A new book on willpower asserts that it's a muscle. That is, you can strengthen it with practice, and you can exhaust it with stress and overuse. This makes sense, and years of research back the idea.

A scientific squabble over how to define self-control draws from an unlikely source: A story from Greek mythology. Sailing home to Ithaca after the Trojan War, Odysseus longed to hear the Sirens’ ...