If it has really drastic effect, you were probably having way too much.
I usually have at least 1 or 2 coffee during the day and occasionally I'll have a Coke or two as well. When I don't, all seems well. If I do, I can still sleep that night. It just doesn't seem to have a dramatic effect on me. If I drink too much caffeine, I get the jitters. I try to stay well away from that limit though.
I didn't drink that much pop, never touched coffee. I just think it's crazy how much it effects me...after not having it for a period of time.
pop = soda ... midwestern thing.
