While your brain will down-regulate norepinephrine and dopamine receptors over time with caffeine usage which will make it less effective and cause addiction and withdrawals, which you've experienced, you probably still have overall higher levels of both neurotransmitters when you drink caffeine when you have a tolerance to it than you would without any at all, even after re-adjusting. It does give a net mental boost and if you're used to that, it can be hard to be satisfied with not having it. You may not be as sharp or on-point once you get used to not having caffeine, but eventually it will feel like thinking normally since you'll get used to it. It's a tradeoff.