Yeah, i know exactly what you mean. And i'm not 18 i'm 57 so it can happen at any age. At 18 you should be out enjoying yourself. get out and do things. Challenge yourself to do things. Meet people. Start to like yourself and feel good about yourself. I think my problem is that i never found anyone that wanted to share my life and life itself became meaningless. I've realised ( yeah i know FINALLY at 57) that unless i make a huge effort and get out and try and find someone i either face a lonely old age or the alternative and we all know what the alternative is. Don't give in to negative thoughts, don't wallow in self pity or melancholy. The minute you think you might, get out and do something. Could be anything. Exercise, go to the shops, help someone,start a task ( even if you do'nt finish it ) whatever. Life ain't easy bud and no ones gonna put it on a plate for you. You gotta go out and get it. good luck.