A former drug addict himself, Lewis now researches addiction. In order to get over ones addiction, he explains, self-trust is necessary.
Unfortunately, self-trust is extremely difficult for an addict to achieve. There are two factors that make it so difficult to get over an addiction: lack of self-control and an inability to put off reward. An addict wants his fix and he wants it now, despite the risk of losing out on a happier, healthier future.
The way to build self-trust, Lewis explained, and get over an addiction is for the addict to begin an internal dialogue with his future self to convince his present self that it can, in fact, live without its addiction.