I know that when I'm very emotional in any way I can't eat. It's like my appetite vanishes. Depression, mania, anxiety, anger... any intense emotion shuts down my appitite. I'm fat so I don't worry much about it, but it messes up my metabolism really bad. It's really hard because food makes me nauseous and everything. Sometimes, thought, when I force myself I feel a bit better after a few bites.

Hamster's suggestions are very good. Even a spoon of peanut butter and 2-3 crackers is better than nothing.