I abused caffeine for years. First it was high-stimulant prework out drinks and cutting supplements. Then I got into "energy drinks" and such. I used to brag that I could drink a liter of Mt. Dew at 10pm and go straight to bed. In 2011, I got off all caffeine entirely in preparation for some international travel, and kept it up for 6 or 8 months before starting to drink tea and coffee again. More recently, I haven't been abusing caffeine like that, but I was drinking three or four coffees every morning, and a coffee every afternoon... and about two weeks ago I felt my chest tighten and my heart pump harder than normal. I went to the doc for a check up - nothing wrong, but he said it was probably caffeine related. That was enough for me. I'm 45, and my body just can't tolerate it any more. So I bought some decaf coffee the other day, and I endured the withdrawal headaches this week, and I'm finally over it. Not to say that I won't have an occasional lightly caffeinated drink... but the days of pumping my body up with it are over.