How can I get my energy and motivation back for my upcoming work?

Two days ago we were announced there would be a made-up class for a certain subject on a certain day. I heard that the class was to be next week, so I prepared for next week. But this morning when I got to class I was informed that the class had already started yesterday! I had misheard the date. To make the matter worse, there was a small test on that day. I tried to talk the teacher round to letting me take that test again but she refused (yeah, I don’t blame the teacher, I think I kind of deserve it), meaning I got a huge 0 for that test.

The thing is, there is going to be a presentation and my group members have to prepare for it, but after that incident I’m now trapped in my self-punishment. I keep blaming myself for my stupidity, saying why the heck I didn’t pay attention back then and filling my mind with negative consequences of how the 0 will affect my result. I know I have to get to work but now I have no energy nor motivation to start working. I know I have to snap out of it but I don’t know how…