I'd tell that miserable 18 year old to just kill himself and not endure another 10 years of agony.
Worst time of my life I felt like I had no options. In reality, its damn well possible I really had no options but down, down, down. Eventually I let all the thoughts in my head and took everything one by one, every problem and dissatisfaction I had I took it and I decided then what i would do with it-- no matter how drastic the change/solution would be, especially if it meant giving up the "few things" i felt I still held on to. Whatever I couldn't solve I scrapped, or put aside temporarily reminding myself to not let it pressure me and stay on my shoulders. people around me are enjoying their lives, why should I be wasting my time? For me, it was eating shit from school, classmates and teachers for my bad grades, attitude and performance but "great potential!" (oh, save it you patronizing assholes), to realizing that I didn't want to go to Princetardvardale an instead found motivation in West Point University, where I saw people I wanted to be who got their asses beat and made it out the other end with a look of strength and purpose that kicked ass in two world wars. You've got a chance, you've got a million chances, to do a million things. Find your motivation, scrap the bs, let the rot go and take whatever you've lost and sacrificed as the price for having everything you couldn't even imagine you could have in a little bit of time. Pardon the ramble, I haven't slept much, I think my point is you gotta find someone or something that's gonna give you a purpose, if you've decided that right now (and 10 years until now) you haven't had one. There are professionals too, good luck friend.