Willpower is not a simple muscle

For years, “ego depletion” offered a tidy story: resisting temptation consumes a limited resource, so later self-control weakens like a tired muscle. Early experiments made the metaphor famous. Larger replication efforts and meta-analytic disputes then found smaller, unstable, or design-sensitive effects, while alternative accounts emphasised motivation, beliefs, and attention.

That does not prove fatigue is imaginary or that every person has endless control. It corrects the certainty of one mechanism. The practical consequence is to avoid treating a lapse as a fuel gauge hitting zero. Sleep, incentives, habits, stress, and available choices can all change what happens next; no single invisible reservoir has earned the whole explanation.