Caffeine Can Only Amplify What's Already There.
You know the feeling. You drink your coffee, get a window of focus, and then it's gone. The second cup does less than the first. The third barely moves the needle.
That's not a caffeine problem. That's a brain foundation problem.
Caffeine doesn't create energy. It blocks the signal that tells your brain it's tired. What it amplifies is whatever you already have underneath — your focus, your clarity, your mental reserves. When your brain foundation is low, caffeine has nothing real to work with. You get stimulation without actual performance.*