My username says it all...I was always the tall and skinny kid. I started lifting weights in high school with 2 of my close friends. We would lift 2 hours a day, 5 days a week, and I never saw the gains I was looking for because I was uneducated about my diet. I stopped working out routinely until I got out of college, and weighed a whopping 165lbs. I joined the Bodybuilding.com forums and started educating myself about proper nutrition and exercise programs for gaining weight. After a few ups and downs, I have managed to transform my body pretty significantly and am always striving for more. I call it "musclerexia."
To me, bodybuilding is 90% mental. It is how it makes you feel about yourself, your self-image. I'm not going to lie, getting compliments from others sure does help the motivation, but you are your own worst critic. If you aren't happy with how you look, nothing that anyone tells you makes a difference. Bodybuilding has helped me make many close friends, more importantly my lifting partner, who is always pushing me both directly and indirectly through his goals and progress. Bodybuilding has changed my life in many ways, and I don't know what I would do without it.