As an example: when I was an addict, and was in severe withdrawals, I would go through the motions and inject saline solution. This would, despite me knowing it

As an example: when I was an addict, and was in severe withdrawals, I would go through the motions and inject saline solution. This would, despite me knowing it's not actually a drug, get rid of my withdrawals for a while; the placebo effect coupled with the "ritual" is very powerful. After I got clean, and the cravings went away, I would still have dreams of injecting drugs; not heroin, but anything. The behaviour was an addiction in and of itself.