If all I think about is how well I do something, or can do something, then I will never get around to finishing what I begin, or my finishing it will smear what good I began. Or I will fall into the failure of repeating what it is I do well.
If all I think about is how bad I do something, I will inevitably be drawn into a fazed and opposite direction; a directionless direction that leads to some danger I know not what, for I will be avoiding some test. This latter mistake is less worse than the former.
Both are parts of the dual problem that proves the efficacy of deciding that it is all going to be done for God's glory. He bears the burden of both failure and success. And success can too often prove the greater burden. He redeems failure and He brings success to the next height. Doing something - everything - for the ultimate glory of God is the most realistic route to take. It brings air and light to what is about to be stifled. It suddenly removes a barrier. Because God takes up both success and failure, one can head forth to another horizon with both failure and success behind one, and still have continuity.
But it must be added: it can be a naked, fierce and frightening thing.