Reb Moshe Feinstein (Igros Moshe Orach Chaim 40) writes, "When walking in the marketplace, everyone has an obligation to look down, but not in the ways of the קיזאי פרושים."
The קיזאי פרושים are mentioned in Sotah 22b. They are people who want to make an impression that they are holy, and that they guard their eyes, but it isn't real. They pretend to be holy to fool people, because they want people to rely on them. The word קיזאי comes from the word דם מקיז, blood-letting. Rashi explains, "He makes himself like he is guarding his eyes, so as not to look at women, and thereby, bumps his head in the wall and blood comes forth."
Reb Moshe says that a person is obligated to guard his eyes while walking in the street, etc., but not to the extent that he will bump his head in the wall.
Face to stop him. At that time, he said this lesson: there is punishment and there is reward, and this realization helped him overcome the yetzer hara.
The Chidushei HaRim elaborated on this lesson some more. The first time it states אֲנִי א ֱלֹק ֵיכֶם 'ה in this pasuk, it refers to the miracles that Hashem performed for us at yetzias Mitzrayim. As it states הוֹצ ֵאתִי ֶׁראֲש א ֱלֹק ֵיכֶם 'ה אֲנִי מ ִצְר ַיִם מֵאֶרֶץ אֶתְכֶם, "I am Hashem, your G-d, Who took you out of the land of Mitzrayim." The purpose was לֵאלֹקִים לָכֶם לִה ְיוֹת, so Hashem will be our G-d. The pasuk concludes, 'ה אֲנִי א ֱלֹק ֵיכֶם. The second time it states א ֱלֹק ֵיכֶם 'ה אֲנִי, it is referring to our times. When a person desires to serve Hashem, Hashem will perform miracles to help him succeed.
The Chidushei HaRim's words are as follows: מצרים מיציאת והנפלאות הניסים כל מתעורר 'ית 'ה לעבוד שרוצה לאדם ועזר לסיוע, "All the miracles and wonders of yetzias Mitzrayim are aroused to help the person who desires to serve Hashem." It is up to him to desire, to try, and then Hashem will help him, even in miraculous ways. He can merit miracles similar to those that occurred at yetzias Mitzrayim, to help him do Hashem's will. It all begins with his desire to do good.
