I find myself believing that the current piece I am working on defines my art and my abilities. In reality, I know that one piece is just a step in the evolution, forward or backward, and cannot speak for an entire body of work. Over time, I have gained faith that my vision will return and cancel any doubt that a difficult piece may foster. This is a lesson that was hard to learn as struggles and failures caused debilitating self doubt to interfere with my progress. I would complete a satisfying painting and have a great nights sleep only to awaken the next morning to see the piece anew and wonder what in the world I was thinking! Every artist I have ever spoken with has had to deal with failure and self-doubt. It is part of the process of evolution, learn from it and move on. At least you are finding out what doesn't work!