I quit coffee as part of New Year's resolution. I started feeling nauseous in the morning if I drank a cup of coffee in the afternoon the day before.

Once I quit, I thought I'll be less productive, and that I won't be able to focus, but after a week or two, my body recovered from the caffeine addiction.

I started drinking black tea - two cups per day. It's still caffeine, but in far less amount.

I miss coffee, though. I miss its smell and taste and somehow I correlate coffee with work satisfaction, creativity, and being productive. It's probably because the coffee is marketed around work culture, and I bought that.