Bad reason: I eat because I'm bored.
I'm a lot better about this than I used to be, but for example, last night after a long day (up at 4:45 with 3 hours of sleep, gym, work, studying for class, 4 hours of class) and getting home 17 hours after I'd left, I just wanted to relax for a bit instead of going to bed. Caught up on a couple shows and ate some Cheez-Its and trail mix (aka mnm's with obstacles).
Killed a heavy chest workout first thing this morning, so I utilized those cals and carbs, but still, that's not a good habit to be in.
Keeping busy and staying on a schedule/routine has helped me tremendously at limiting my snacking. I've also found that I don't tend to do that as much when I'm with other people vs. when I'm just alone at the house.