You have to think of yourself, if he wants to self destruct leave him to it. You just have to remind yourself when things go south that its not your fault, its his. My partner has a habit of doing stupid things and every time I start to feel sorry for.him I tell myself 'its his own fault, dont feel sorry for him' and I dont get pulled into his bull****. There is only so much you can try and help someone before it starts affecting your quality of life and you have passed that line a long time ago. Please start looking after yourself, just remember you are important as well.