I suffered from this for performing on guitar and you can read the embarrassing story of how I overcome this here:
Antidote to Perfectionism
Frustration is actually a good sign. It shows that you are at the limit of your ability and striving to do more. At this limit failure comes often and that disappoints us and causes frustration. Accepting that frustration is a good thing and part of the process of learning is a helpful step in the right direction. In order to take better control of the situation so that you don't enormously frustrated and then witness a decrease in ability you might find this article useful:
Supercharge Your Learning Pt.I
I sympathize greatly and rest assured that you are on the verge of a breakthrough. All you need to do is adjust how you interpret frustration and prepare yourself better for the inevitable frustration to come and you will find yourself improving much more rapidly and much more able to take setbacks in your stride.