One study I read displayed two groups: A and B. Group A had addicts shooting actual heroin when withdrawal time came. Group B was the same except a placebo was given instead of actual heroin. It was shown that in group B, many patients showed relief once done injecting. Besides this study, by talking to old-timers in the methadone clinic I discovered that a lot of ppl were both obsessed and addicted with the needle. They loved it. A number explained that getting that drug would first help them out, then using the needle finally helped them out of their sickness.
When I using, I was kinda like Group B for a while. Nonetheless, if I knew I got fake heroin, (which I usually sussed before I actually used it) I would not get high off it. Sometimes I would not get high at all and wonder if I got fake heroin. Those times it was usually low-quality heroin.
It's tough, but you can beat your addiction, or obsession, with the needle. I won't bother you with the there are better things out there thing which you have probably heard enough (it's still cool tho); instead something practical: try something completely new or out of the ordinary. It can be anything (just not needle/drug related). It will take your mind off the needle. This exercise is useful if you have OCD, albeit some limitations. In the short term, it works like a charm. I began keeping a journal. I still keep it to this day.
Good luck and hang in there,
mandraxx