Why do my legs shake when im nervous ?

the thing Similiar to Meeting Justin WarnER and Taylor Hanson is that I shook like a leaf .. I dont know why really - maybe because I wanted to be perfect and Said what I had dreamed of .. which didnt happen on the first trys at all . but at least I had the courage to talk -- thats  the most important thing . I was able to say thank you without  seeming like a over zeaolous fan . heres my fave pic of the 2012 Food Net work star season . said pictures reminds me  of Taylor and i .. and forever greatful he  and Alton took the chance :  I had  Justin Sign this Picture and he said " " I 'll start to tear up if I look at that anymore " thats so ME !