I'm immune to caffeine. I drink diet coke and coffee all day long. I do have occasional problems sleeping but it seems unrelated to caffeine consumption; drinking more or less in a given day does not coincide with sleeplessness, though my stress of that day will.
I mean, we gotta give up cigarettes, and drinks, and pot, and sex, and preservatives
and processed flour products, and any food that tastes good. Caffeine will be my last bastion of viceness!