@thibaultamartin My experience is the opposite - I almost always feel better after a cup of coffee, and in periods when I drink more coffee I feel better than when I drink less. It's not due to addiction - I do not drink coffee every day, and I never suffer from it's absence. But a nice cup of coffee never fails to lighten my day.

There must be individual differences like with everything else. Caffeine is just part of it - it's the ritual, the smell, the taste, the break, the warmth. ☕