Breaking My Caffeine Addiction

So I'm trying to cut back on caffeine, reducing my intake from two to three diet sodas a day to just one in the morning. I'm not sure why I'm doing it, but people have told me that when they've quit caffeine they feel great and full of energy, etc. I've been down to one soda a day for a few weeks now, and I don't have any "cravings" for caffeine, but I also don't feel great or energetic. The afternoons seem especially slow and tend to drag on forever, and I don't feel as sharp as I used to after drinking a soda. So, I'm not sure this caffeine-free existence is for me.