We all struggle with negative thoughts, negative feelings, and negative actions. I cannot think of one single person who is 100% positive energy, 100% of the time. But I can think of scores of people who allow negativity to dominate their life. People who complain. People who only see the worst in every situation. And you will, too, if you allow negativity in your life.
Instead, make an effort every day to think positively. Find the good in every situation. Because whatever situation you find yourself in, there is always a silver lining. There is always something to be thankful for. That something may not be immediately obvious. But it is there. Find it. Be positive.