Disappointment in myself

Sometimes...I feel so disappointed in myself....I know and knew I could do better...way better and somehow I just screw it over. I read tests too fast and end up screwing up the answers  becasuse I didn't read it carefully. Today I was suppose to sing for Jackie as practice with her boyfriend, Diego, there. -Sigh- I totally don't know what's wrong with me...Why am I so nervous to sing in front of people? Why? Seriously? I got so nervous that even though I know I can sing, I cracked. Fuck mann. Sometimes the things I'm good at...I wish I could just be super good and get over the damn nervousness, but I don't know how. I did before, but I haven't sang in front of people in awhile so it makes me nervous all over again. Ehhh...and I'm sososo tired of benchmarks and finals...I bet you I bombed the chemistry one today because it was just really hard....I'm so tired of being not good and then sucking at my talents when people are there. What is wrong with me?...