Appetite is an interesting thing. Under certain circumstances, you simply cannot eat or aren't hungry. For instance, you're really stressed out, your stomach twists into knots and you might munch to relieve stress but you're genuinely not hungry. Or when you're nervous the same thing happens. Or when you're really excited about something, you're brain goes in every which direction and you're not hungry; all you can do is think and thinking about food is not enticing. It's also weird how there's mindless eating, like when you're watching t.v. or reading or doing homework. It's interesting that it's not consistent.