I'm with you buddy. Never was smack for me, but pot and alcohol did their worst with me. The alcohol and drugs kill the feelings, and then when you stop them you have to deal with those feelings which drives you back to the alcohol and drugs. The vicious cycle of addiction.
I'm now 16 years sober/clean. A 12 step group has been critical to help me avert relapses. Intensive therapy has been helping me deal with the pain, anger, shame, fear, and self hate.
Good to hear that you are going to start N/A. There is a Heroin-Anonymous.org organization as well that might have a branch near you.
One piece of advice there-in: The benefit of a 12 step group isn't just in attending meetings (although that helps), its in sharing your, and listening to others, struggles, experience, and hope, honestly and openly. I see a lot of people (including myself in the past) come to meetings but never talk to anyone, never get a sponsor, never really take advantage of all the program has to offer. If you commit to a 12 step group, take it all the way. You can only benefit from it.
"But now old friends are acting strange,
they shake their heads, they say I've changed.
Something's lost but something's gained in living every day
....it's life's illusions I recall, I really don't know life at all. "Joni Mitchell