I've always had issues with focus, and first year of college was overwhelming. I cut out all unnecessary time sinks, and I've found that I lack enough "focus" in a day - at some point I'd just read, but be unable to engage with any words I'm reading.

Caffeine pills helped me study for longer, however, the tolerance made me take more and more until at some point I was taking up to 2000mg of caffeine a day. I was barely functioning from anxiety, but I managed to be amongst better students on my year.

At work we have an espresso machine, so it's very easy to just "grab a cup" when I feel tired while working on an important task. It wasn't strange for me to drink 5-6 cups per day.

Nowdays, I'm only drinking coffee if it's a social event, and I keep a hard limit of one cup per day.