You just feel better overall, physically and mentally. Not to sound narcissistic, but the amount of compliments and double-takes you get is a huge confidence booster. People will take note of your transformation more easily than you will. Even after a rough night of no sleep, after hitting the gym in the morning, coworkers will tell me I'm "glowing" (lol, women of course) or that my aura is stronger...even though I feel like crap on the inside!
And yes, it becomes routine/habit/lifestyle after a while. I go to the gym every morning before work, and if I miss a day, my whole day seems completely thrown off.