My 19 yr old daughter went through her first rebellion last year (no addictions) and told me she wanted nothing to do with me. I was heartbroken and shocked but said "ok, I will respect your wishes." At first, I cried a lot then it became easier. Personally, I am now glad I didn't have to be witness to her silly choices like being engaged at 18, etc.
Everyone told me she would come back and she has. She and I needed to detach some and I think in some ways this was her way to claim her independence. Also, she has anger issues towards her birth mother to work out and I was the safe one.
She had scholarships to college, yet chose not to go. That was driving me crazy. But I guess she wasn't ready, it will never be too late and I was forced to accept that. The best part is I have. It's her life and I am relieved I am not trying to micromanage it any more. Heck, I have enough trouble with my own.
The slogan "Let go and let God" was my saving grace.