Recently, one of my students brought me a Czerny etude. He is a diligent student and is in the final stages of completing the piece, but he was having trouble getting through it without making any mistakes. He said that he had been able to do it when practicing at home, so when I asked him about it, he said that he could do it if he completed the entire practice and put it through at the end.
In such cases, what is needed is practice that will carry over to the next day. When you go through the piece at the end of the practice session, sharpen your senses, memorize the feeling of how you are playing, and if you play well, be conscious of not forgetting it until the next day. Then, at the beginning of the next day's practice, try to play through the piece right away, concentrating all your energy on playing to reproduce exactly how you played well the day before. This "reproduction" is not necessarily easy, but by repeatedly practicing with this kind of awareness, I believe you will definitely be able to do it.