That happens sometimes. Nothing I can tell you can make you do what you need to do. It's something you have to take in stride. Think about it, you got an A on the first report so why worry now? You're at the end of it you're almost finished. Maybe finishing something is what worries you? You just have to really tell yourself that you can do this, motivate yourself and just do it. Don't even think about it but at the same time focus on that one task and get it done. You've proven you can do it, so finish it off, I am sure you will be just fine.

Best of luck.