Anxiety spiraling about kid's school performance

My 7yo got a B on his math test and I literally couldn't sleep last night. I kept thinking about how he's going to fall behind, not get into a good middle school, etc. My wife finally had to tell me to shut up at 2am. I KNOW I'm being irrational but I can't turn my brain off. Has anyone else dealt with this? How do you stop catastrophizing about stuff that probably won't happen? I'm exhausted from my own thoughts.