Caffeine has a wide variety of effects in the body. Mechanistically, some of the effects are direct (such as Caffeine acting as an Adenosine Antagonist, the molecule literally blocks the receptor) and others are indirect (any effects on dopamine are ‘downstream’ of the reaction with adenosine, like the latter aspects of a Domino cascade). When tolerance develops to caffeine
Source: Do I need to cycle caffeine?
If you have “brutal” headaches when you don’t get your regular dose of caffeine, that’s when you need to cycle it down.