Caffeine and depression
I've read that caffeine withdrawal includes depression. I've noticed that every time I stop drinking caffeinated coffee, I feel very depressed even after all the withdrawal symptoms have passed (headache, extreme fatigue, etc.). Even if I don't drink it for a while, I feel a very noticable perk in my mood when I drink a cup one morning.
I don't want to rely on caffeine to feel good and think clearly, but I can't stand feeling this way either.