Negativity surrounds us, but that doesn't mean that we have to let it penetrate our being and effect our state of mind. When I find myself engulfed by negativity, I remind myself of what my guru says, and focus on the positive. When you think positive thoughts and feel gratitude it leaves no room for negative ones.
Swami Sivananda words on how to subdue negative thoughts:
"Learn to subdue, to purify, to order all your thoughts. Fight against all negative thoughts and doubts. Let sublime thoughts come to you from every side. Thoughts of depression, failure, weakness, darkness, doubts, fear etc. are negative thoughts. Cultivate positive thoughts of strength, courage, love, contentment and cheerfulness. The negative thoughts will disappear."