A Jew really has two struggles in life. The first is the recognition that G-d Himself created evil in the world. This is proven from the Book of Isaiah 46:7 where it's written, עושה שלום ובורא רע, that Hashem created peace and evil. It is our task to recognize evil wherever it appears and separate ourselves from it. This evil can be present both among Jews and non-Jews. We are rewarded for separating from it and punished if we succumb to it. The second struggle is between טומאה and טהרה, purity and impurity. This, too, is difficult as it's often not so clear what is purity and what is impurity. Most feel that we win this struggle by way of separation. If we try to live lives of holiness and we worship Hashem and observe the Mitzvot with enthusiasm, we will be elevated to higher levels of purity. טומאה is not necessarily evil, but it does have the effect of decreasing sanctity. The awareness of our mission to stay away from evil and impurities, will allow us to conquer them.