I gave up coffee a few months ago too. I was following the 5:2 reduced calorie diet, which having only 600kcal on two non-consecutive days a week. I like coffee with milk and sugar, which was too many calories, so I was going without two days a week. I found that gave me headaches from caffeine withdrawal. Knowing I was affected to that extent bothered me enough to drop coffee altogether.

As it happens, I didn't miss it; I guess I don't have an addictive personality. However, I still haven't found anything great to replace it with. I mention it here because I sometimes make low-cal fruit squash with boiling water. I find this has more flavour than herbal teas.