1g of caffeine is high, but with tolerance it doesn't seem _that_ high. I currently use 600mg/day to help with OCD[1], and it doesn't really effect me - heart rate barely moves, and I don't feel noticeably different. I've tried 1g, and it made me feel _slightly_ jittery, but that was about it.

[1] Counter-intuitive I know, but it seems to help - it makes the intrusive thoughts easier to ignore