Know and repeat often, that which Chazal say (Avos 4:5)  “One sin brings on another sin, and one mitzvah brings more mitzvos.” If you will satisfy temptation once, you will desire them many more times. But if you will be a warrior and conquer your yetzer hara and turn your eyes from seeing evil one time, it will be easy for you to do so several times. ~ Sefer HaChinuch, Mitzvah 387