In addition to the tips given by R3SsH|n,
I think it's a confidence situation and the negative thoughts that cross our minds that create this kanjiongness.
No confidence

don't believe can succeed

negative thoughts start to flood the mind

instead of focusing on task at hand, focus instead on "how i am going to fail" and "what is going to happen when i fail".
Thus, when we don't focus on what we are doing, especially things we are new to or not that comfortable with, the chances of mucking it up increases.
So I say,
focus on the task at hand. Do it as well as you can. Must learn to master the mind, and not let it wander and let useless thoughts creep into our heads.
Confidence need to slowly train up. Real confidence cannot be faked, it has to be nurtured. It's a deep seated belief in oneself. And it can only come with more experience with success. So it is actually good to expose ourselves to situations that we are not comfortable with and figure out a way to deal with them.