Unfortunately, there is nothing you can do. The more you try to give him advice, the more he's going to shut you out. Since he's almost 18, he probably feels like he is old enough to make his own decisions about everything, and doesn't look at it as you being wiser than he. My brother was absolutely nuts with partying at that age, and no matter what we tried to do, he just blew us off. He joined the army to have a purpose in life, and after deciding he wanted out, he, in his lost mind, "staged" a suicide attempt. They let him out after a psych evaluation, and then he decided the best thing for him would be to sell everything he owned, drive out west with his pitbull, and find someone to let him live off his land for a year because he wanted to "escape" from society for awhile. The reason I'm bringing these things up to you is because even when he was throwing these completely OFF THE WALL things out there at us, there was still nothing at all that we could do. Believe me, I tried. The only person who didn't have the personality type to fight his weird ideas was my mother. And I'll tell you what, for years and years, he really counted on her because she always stood by him. I would get so mad at her, but in the end, her getting mad wouldn't have made a distance, and throughout the whole thing, she was always his constant in his life. As far as me, our sister, and our dad go though, he thought he had all the answers, and wasn't about to let anyone have a say in his life. Guys are just different than girls. They mature a lot later for the most part, but yet get all of the adult freedom at the same time as girls. So, it's kinda like a little kid in a candy store with no adults around. As hard as it was for us, we just had to let him go. We just prayed that he would grow up soon, and realize that what he was doing with his life was totally absurd. He's now 29, and just got married for the second time, has a second child on the way, and his wife is wonderful (a very pleasant surprise to all of us)! My brother still has things about him that prove he's got the maturity level of an 18 year old, but atleast he has a good life now. Even now, 10 years after the weird army and out west thing, I still don't hold my breath with him. I mean, he's still messing up his life all the time. I mean only a year ago, he had a girl knocked up, 9 years younger than him (his current wife now though) before he was even divorced! As a matter of fact, he asked her to marry him while he was still married. Now, don't get scared, there were drugs involved with my brother's downward spiral, but atleast you get the picture of how much you really cannot help them. They really do need to learn everything on their own, including those mistakes that you see coming like a freight train. If your son and his girlfriend are not meant to be together, he will figure that out. The best you can do is always be there for him when he needs you. The more you lay off of him with stuff you disagree with, the more likely he is to keep you involved and to come to you when things go bad. He won't be as likely to if you are negative about stuff all along because the last thing we all want to subject ourselves to is a big "I told you so". Even if it isn't said, it's still something that he will be aware of because eventually he'll be ashamed he didn't listen to you in the first place.