You don’t have to look very far to find plenty to be negative about, but why would you choose to feel bad when you could choose to feel good? Every moment of every day that you are awake you have complete freedom to choose how you feel.
When you choose to find something in your field of reality that makes you feel good, you will observe/find/attract more awareness of other things you can feel good about. As you observe more to feel good about, what you think about seems to expand in your reality. Soon you see even more to feel good about.
Napoleon Hill wrote that the human being has only one thing he or she has complete control over, but that the one thing was sufficient to control all the other aspects of their life. That one thing, he said, was the power over their choice of what to think. He went on to write the classic manifestation manual “Think and Grow Rich”.
The principle of choosing your thoughts is basic to many spiritual disciplines, ancient and 21st century. Despite improvements in the physical aspect of modern life, the original laws of manifestation are the same today as then. As you believe, so it is given unto you. You get what you set.
So, why be positive? Number one, because you can. Number two, because when you look for positive you see, or perhaps create, more positive. Unlike magnetism, in manifestation Like attracts Like.