Happiness is getting done with your meetings early;
Happiness is finding an earlier, more convenient flight than the late one on which you were previously scheduled;
Happiness is just how user-friendly the Kansas City airport seems to be. The counter is right next to the security checkpoint, there's a serviceable Mexican place right next to my gate, and the beer, she is cold. Moreover, the in-airport wi-fi is simple -- one click baby -- without any of the nonsense you usually have to deal with.
Happiness is being able to be home in time to catch the Sox-Twins game.
Business travel stinks, but the happiness bar is set so low that it's not hard to feel really good about it if just a couple of things break right.