You have to realize there is nothing more you can do to...

You have to realize there is nothing more you can do to convince someone you love to turn their life around. You simply have to say, "Look. I love you, but I cannot stand by and watch you kill yourself slowly. When you want help I'm here. Until then, goodbye." That may sound cruel, but self-preservation is paramount to helping someone else. If you're a wreck, you're useless to them, anyway. And if they refuse help, despite knowing the likely outcome, they will head down that path anyway.