I think people commonly believe that they bodybuild because they love it. For those who have been doing this for a while, he or she may start to sense that it's also possible that they love bodybuilding because he or she does it. You can especially sense the latter when you go to the gym despite feeling like your not in the mood for it and as you get into your workout, you start to feel turned on and you have a great workout. Or maybe you were never into the workout and no matter what, your just not into it that day. Yet, you remain commited overall to that principle that is the bodybuilding lifestyle.
I think the same basic idea applies to relationships as well. You don't always feel profound love but you know that you have to act loving at all times to maintain this relationship. As you mature you start to go beyond simple, immediate emotions. Can you relate to what I'm saying here?