Effective self-regulation is an important key to successful functioning in many spheres, and failed self-regulation may be centrally conducive to substance abuse and addiction. The program of research summarized here indicates that self-regulation operates as a limited resource, akin to strength or energy, especially insofar as it becomes depleted after use-leaving the depleted self subsequently vulnerable to impulsive and undercontrolled behaviors (including increased consumption of alcohol). The self's resources, which are also used for decision-making and active responding, can be replenished by rest and positive emotions.