Caffeine Makes Me Grumpy

I think I've discovered that caffeine makes me irritable. I've been drinking caffeine in the morning for a long time now. Lately, though, I would have some in the afternoon for a pick-me-up. I'm not sure if it's the caffeine that actually makes me irritable or the fact that I am already tired that is why I'm grumpy. I will have to experiment and see what results I will with the following afternoon scenarios:
a. tired and caffeine loaded
b. tired but refraining from caffeine
c. not tired but caffeine loaded
d. not tired and refraining from caffeine

If I find that it in indeed the caffeine that makes me irritable, then I will know to stay out of caffeine loaded products like those strongest fat burners.

Right now, I am sooo tired but the shot of espresso I had earlier in the afternoon is still affecting me. My body is tired but my mind is still racing. Sigh.