Please help! I'm terrified!?

I'm a perfectionist and I'm in grade 8. I got back a math test last week and i got SEVENTY FOUR! AHHHHHH!!! I am horrified! I made a whole bunch of dumb mistakes which all put together made a big difference on the test. My mom just asked me about 5 minutes ago what I got on the test and I just said that I don't know yet because I was too sad to tell her anything! My poor mother! I've let her down! I'm a terrible person! What will I do! Report cards are coming next week! I need some soothing words!