Read this article, it should be very insightful to long term opiate usage.
http://neuro.psychiatryonline.org/article.aspx?articleid=103089
Basically just causes a cognitive deficiency (your brain won't work as quickly or efficiently as it should) but really that's with anything you abuse. Two years is not the worst case out there, there are some folks who have been on opiates (like myself) for a long time 5+ years and I have been able to heal and kick my lack of control. I feel just as good as ever right now, but I probably would be physically a bit better off if I had used a lot less. You will be okay, I can assure you. You will always have sort of a residual psycological tolerance to opiates, each time you use them it brings about a great sense of tolerance to them, even if you wait a while. Needless to say, don't wait six months to do your normal "high" dose, because you might kick the bucket, but mentally it won't take long to build back up to that as opposed to an average person.
If you really don't have the willpower to be a "weekend type" user, then you really should stay away. I had to stay away for a while, but I came to terms and realized I can't feel that good all the time, and I should just wait and do it every once in a while so I can still keep some of that "magic" going you know? Doing it everyday, you feel good, but you know how it is, it just gets shitty after a while and boring, expensive, and ends up being a pain in the ass with withdrawals.
You would be really suprised what the mind can do. Stay strong...positive reinforcement. Your post showed up just fine obviously lol. If you are able to get on the computer, talk to me about this, and recognize your problem, and are actively trying to confront it, you are already miles ahead of most man. Good for you