I have a big fear!!

Before a contest, i become extremely nervous to give the contest or not(very much scared of rating downfall)

Moreover I feel that I have attained my best rating(upto what is my potential) and should now focus on increasing my level(doing >= 1600 in my case) and then start giving contests when i am comfortable on this range . **** Does this notion work or I should do something else to increase my performance?

And also it would be extremely helpful to guide to how to maintain coolness in a contest

Thanks