I don't always feel exceedingly hungry with the standard rumbly stomach, so sometimes it creeps up on me. Then I'm suddenly irritable and my head's hurting and I can't figure out why I'm so shaky. Eating usually remedies this.
The only time I feel sad or depressed after eating is when I've spent a good deal of money on a fancy meal. Then I think, "I would have been just as full if I'd cooked veggies at home, and I could have spent that money on something that lasts longer than 30 minutes."