Well in my case, I'm the spouse that got better and my wife is the one who stuck by me so yes, it does happen and I'm living with about 3.5 years of sobriety now. However, as others have stated, your BF's recovery is 100% dependent on his willingness and perseverance to live 1 day at a time in sobriety and face his own circumstances. I've talked about dual diagnoses therapists before and how they approach psychologic conditions and addiction as co-conditions that feed on each other is a cyclical manner. You feel bad, which makes you take your chosen substance, which makes you feel worse, which makes you take more and so on and so on. As for your part, perhaps the only thing you can do if you want to, is tell him that you want to support him, but in the end it is conditional on his sobriety. You are not a bad person for stepping away if he can't do that and it isn't your fault if he chooses his addiction. I think the worst thing for you and him would be to allow your relationship to be an enabling one.