Mental time travel is constantly taking us off the frontier of the present moment. This can be highly adaptive; it allows us to learn from the past and plan for the future. But when time travel turns obsessive, it fosters the backward-looking gaze of depression and the forward pitch of anxiety. Addiction, too, seems to involve uncontrollable time travel. The addict uses his habit to organize time: When was the last hit, and when can I get the next?
