I follow a workout inspiration blog (aptly named Workout Inspiration) and they often have posts about a guy named Greg Plitt, who I suppose is some sort of fitness guru who is really all about giving your all, all the time. One of the things that he said in the latest post was "The pain you feel today becomes the peace you feel tomorrow." The blog certainly lives up to its name -- inspirational.
Admittedly I have never bought any of Plitt's DVD's, or even really looked at any of his workouts, or tried any exercises that he says (I remember one specifically because I don't have any kettleballs at home, and thus can't do anything in that regard).
That's the way I'd like to be with my workouts though, completely motivated and driven to do better, always push the limit, always improve, always bump up the weight. When you think you can't do any more, you do. I always enjoyed running because of that. You'd be dead, but you still had to get home from your run -- and so you pushed yourself and finished the last mile. It might take you awhile, but you'd still do it (certainly helps when there are other people to run with).
So yes, the pain you feel today becomes the peace you feel tomorrow (or perhaps the soreness... haha). In the end it's all worth it. Put yourself through the physical pain of fitness, and you look better, feel better, and in general just get more out of life. Am I right?!