This. So much this.
Yep- one of the moments I chuckle at is when I woke up 15 mins after an exam started (had been studying until 4am, exam was at 9-10am), and I thought I was done for. The exam was 40% of the final course grade! But it's amazing- Adrenaline kicked in, I was in the exam room within 10 mins (it was on the other side of campus) and still had about 35 mins to finish it.
I actually ended up finishing it right as the period ended. Earned a B+ on it. My point is- don't worry about these things until you have to, and then, put it in perspective.
Yikes. Does everyone in your class feel this way about Fall D1?