I used to do Thai Boxing when i was at University, and naturally there were some bigger guys. To cut a long story short i started weight training, eventually moving onto a proper program such as Bill Starrs 5x5 with MANY squats, deadlifts and overhead presses, and from 2008 to now, 2012, i have gone from roughly 149lbs to 210lbs.

I used to be incredibly weak, barely lifting 60kg on bench press and with a max deadlift of 120kg, but now i can lift almost double what i started with, and there's still a way to go! :)

You get a sense of achievement everytime you hit a goal, get more reps or lift more weight. When people complement you it increased your self-confidence and you feel positive.