You are running a high fever or have a massive headache, so know you are going to max out at 4g/day. At that point, it's kind of hard to keep track of the clock.

"My head is pounding. Shit...did I take this at 3PM or 5PM? I know I took it and then fell asleep, but I can't remember when. It is now 9PM, can I take more or not?"