My ADHD husband wants to leave the marriage

My husband is ADHD and I'm not; we've been married for 17 years and have 2 children. He told me last night that he wants to leave the marriage. I'm devastated and am shaking.

During the summers he does a lot of boating with his boating friends. They're a community who likes to tie their cruiser boats together and camp all weekend. It seems to provide the perfect sensory overload that makes him feel at peace: lots of people around, music from each boat, drinking, partying. He said he wants to find someone who is more like him, who likes to party like that.

I am so sad to lose him and am so sad for our children. I told him that I love him. This is hell like I've never felt.