And that's all there is to it.
I do believe dislike of your own work is a good fuel for practice, and a good carrot to try harder. One must not be disheartened by failure, merely strive onwards and rather one should be happy; it is when one cannot improve, when you hit the wall, that worry should set in. A road is usually long and hard when the goal is precious. And that's fine. Perhaps we need to be humble to achieve but at the same time, confidence or perhaps faith is important as well.
I guess when you're displeased, you can do one thing only and that is to improve the object of your displeasure. Seeing a mistake is good, because then you can correct it. When this has been accomplished, a new mistake will rise. And that's fine, too. Resistance is not the enemy of success, it is stagnation one should truly fear. I suppose one can do little more than keep going. And going. As long as you walk, you will arrive somewhere.