Actually, I mean that how my body functions is unaffected by my caffeine intake. If I don't have coffee on any given day, I continue to be functional ... in th

Actually, I mean that how my body functions is unaffected by my caffeine intake. If I don't have coffee on any given day, I continue to be functional ... in the "old days", I'd have had a killer headache within 30-45 minutes of waking up if I didn't down a large cup.