There really is something amazing about the way you feel after working out.
The endorphins kick in, and, instead of feeling tired after the gym, I feel energized and excited! I am really happy that I've gotten to the point where working out is enjoyable--it still takes a while for me to force myself to pull on my shoes and go, but by the time I leave my apartment, I am eager as can be.
After going to the gym, I also feel more motivated to do other things: I want to eat healthier, I want to take care of errands. This is probably why I prefer going to the gym first thing in the morning; that way, my whole day starts off right and I am energized to boot.
Even if I don't accomplish anything else major during the day, I feel as though I have done something really good for myself, and that goes a long way!
And so, on that note, I go forth to be productive and buy a book (the new Dan Brown one--whee!) and walk about Manhattan with this lovely burst of energy.