My first experience with body-building was through a family friend who had been a competitive body-builder before being paralyzed in an accident. Unfortunately, I never really got into it until years later after I'd been in the Army for several years, and had put on a bunch of extra weight.

#1: I love the sense of accomplishment you feel when you say "today I'm going to bench so many pounds for so many reps", and you do it.
#2: I love the way my whole body feels after I finish a good session in the weight-room.