Set your boundaries and stick to them. For me that meant telling my AH that I would not be around him when he was drinking. That drinking was a deal killer for our marriage. We separated.
Fast forward a year. I have not seen my AH drink alcohol in 14 months, but of course he's still drinking. Yesterday I went to his house to have July 4th dinner with him and the kids. I arrived and there was a beer open on the counter. I nearly fell over. I decided to just say nothing as I wasn't up to a confrontation, and part of me was thinking about the whole "I can't control him" thing I've learned in Al Anon (but what I forgot is that I CAN control myself!). The evening was fine and we had a good time. But the open beer really bugged me.
When I got home and sat quietly and thought about it, what I should have done is stuck to my boundary. I should have quietly said "It's great to see you, but if you plan to drink around me I am going to take the kids and go home."
I have found that setting and really keeping those boundaries (and it's hard) is key to my sanity.