The material world is a world of duality: hot and cold, male and female, light and dark, negative and positive.  And it is the coming together, the interactions, of the two opposite forces that makes things happen and creates new things.   I think nearly everybody understands that.  Yet there are some people including some self-help gurus who either teach there there is no negative, only things we don't understand, or that we should ignore the negative and just pay attention to the positive.  
    Let's look at an obvious example of that philosophy.  When Hitler started gaining power, first in Germany, then neighboring countries, he was largely ignored by the rest of the world.  At a time when he might have been stopped with very few lives lost, no one did anything.  They didn't want to acknowledge the negative.  As a result, Hitler continued to gain power until a world war was the only way to stop him and many millions died.  
    Other examples are the way scientists and engineers will come up with ideas for something new and rush to develop it because they think only of the positive benefits.  Soon, however, the military types get their scientists to turn it into a weapon and the initial developer is shocked: he never expected his great invention to be a weapon of war because he looked only at the positive aspects and ignored the negative.  
    In general, if we look only at the positive and ignore the negative, we miss virtually all opportunities to correct problems and make things better.  And I think we can all agree that this is not a perfect world so there is room for improvement.