Years ago, I lived in a building in a large city. The building next door was only a few feet away from mine. There was a woman who lived there, whom I had never met, yet I could see her seated by her window each afternoon, sewing or reading.
After several months went by, I began to notice that her window was dirty. Everything was unclear through the dirty window. I often said to myself, "I wonder why that woman doesn't wash her window. It really looks terrible."
One bright morning I decided to clean my flat, including washing the window on the inside.
Late in the afternoon when I finished the cleaning, I sat down by the window with a cup of coffee for a rest. What a surprise! Across the way, the woman sitting by her window was clearly seen. Her window was clean!
Then _ . I was always criticizing  her dirty window, but all the time I was watching hers through my own dirty window.
That was quite an important lesson for me. How often had I looked at and criticized others through the dirty window of my heart, through my own mistake?
Since then, whenever I wanted to judge  someone, I asked myself first, "Am I looking at him through my own dirty window?"
Then I try to clean the window of my own world so that I may see the world around me more clearly and correctly.
From the passage, we can learn   _  .
one shouldn't criticize others very often one should often make his windows clean one must judge himself before he judges others one must look at others through his dirty windows