It's amazing how much hunger affects mood, more so than I ever had realized before I came to this lifestyle. On days when I haven't eaten enough I'll find that I'm usually somewhat depressed to just plain out angry at the world. At the back of my mind, I try and tell myself "Eat more fruit! You'll feel sooo much better, Michelle!" but I hardly ever want to hear that when I'm upset. Sure enough, though, give me a banana smoothie, and 15 minutes later I'm feelin' on top of the world.
Of course, there are many other factors that affect mood, i.e. getting enough sleep, drinking enough water, etc. but getting enough fruit cals is a HUGE one.
Eat more fruit for health, vitality, and your sanity :)