Why do I always cram?

I always tell myself that I will allow at least for days to study for an exam, but I always let it come down to the wire, the day before, and the day of. Why do I do this? I think because the material is usually intimidating and overwhelming. Thankfully, it rained today; I skipped my history class( which im not happy about) and stayed in bed all morning and studied. Im not done yet but I studied for 4 hours with no break, so im taking one now. I have work at 3 today and I wont be home until midnight.. so its going to be a late one. ughh.