Try this experiment: go into a pitch-black room, like a cellar or a bomb shelter with the lights off. Take a pack of matches with you and light a match. Better yet, light a small candle. Notice how one tiny flame illuminates so much darkness.
The above phenomenon is a wonderful spiritual metaphor: sure, there are tons of evil in the world - wherever you go, wherever you look. But, one righteous person engaged in charitable deeds and in spreading love, peace and joy virtually purifies the atmosphere. The Gemara teaches that such a person can save the world.
You, cherished friend, have every attribute to be that person. Even if you regard yourself as nothing more than one tiny light, you can illuminate the darkness, if you only believe in your ability to do so.