It's not about ceasing to care, or pretending everything is fine, or making the pain "go away." It's about accepting what is and continuing to live your life anyway. It's about learning where you end and another begins.
It's quite possible that he could make choices that wreck his life. But, it's entirely up to you if you let those choices wreck yours.
I understand that you may not find much credibility in my words because I only married an alcoholic. I was married to him for twenty years and my entire life once revolved around him. It's true that I do not know the pain of having an addicted child, at least not so far. And I hope I never know what it's like to be in your shoes. I do know what it's like to lose myself to someone else's addiction, though. I found my way back and I believe you can, too.
L