I just quit caffeine a few weeks back. I still drink it every once and a while. Basically, I was finding I NEEDED a Diet Pepsi every morning or I got really cranky and a headache would come.
So I cut myself off in the mornings in favor of a mug full of cold water.
What's weird is that when I do drink a Diet Pepsi, Mountain Dew or a Diet Coke, a tremendous sense of relief comes over me.