From Zen Mind, Beginner’s Mind:
After you have practiced for a while, you will realize that it is not possible to make rapid, extraordinary progress. Even though you try very hard, the progress you make is always little by little. It is not like going out in a shower in which you know when you get wet. In a fog, you do not know you are getting wet, but as you keep walking you get wet little by little. If your mind has ideas of progress, you may say, “Oh, this pace is terrible!” But actually it is not. When you get wet in a fog it is very difficult to dry yourself. So there is no need to worry about progress. It is like studying a foreign language; you cannot do it all of a sudden, but by repeating it over and over until you master it.
Also known as the Groundhog Day theory of self-improvement.