I put too much pressure on myself?

I always get really upset if I don't do something well. If I mess up in softball I cry and get really upset worrying that if we lose, it will be my fault. I am a straight A student as well ranked, top of my class, but now i'm #2 and kind of upset. I got all A+ and i feel like all that hard work was for nothing and made me go down. I get really frustrated sometimes when i don't get something and break down. I pressure myself not to cry over the littlest things, but i end up breaking down anyways. I really do want to be top of my class, but how can i convince myself that it's okay to make mistakes and try not to cry over the littlest things?