Implementation intentions are if-then plans that spell out when, where, and how a set goal has to be put into action: If situation x is encountered, then I will perform behavior y!, thereby linking a critical situation with a goal-directed behavior. Over the last fifteen years, implementation intentions, as compared to simple goal intentions (I intend to reach z!), have demonstrated their effectiveness as self-regulation strategies in promoting desired behaviors or when unpleasant actions have to be carried out. By forming implementation intentions, the control of unwanted influences (e.g., temptations, bad habits, adverse self-states) on an ongoing goal pursuit can also be facilitated. Furthermore, implementation intentions have been shown to ease goal-directed actions in critical populations such as patients with a frontal brain lesion, schizophrenic patients, and opiate addicts in withdrawal, for whom the initiation problems of the goaldirected action are more accentuated.