Environment is stronger than will. If we observe closely it does diffuse in to our thinking. And we become what we think often, what we become passionate about, what we love or hate. The choice is always ours to avoid negativity.
Often we focus on mistakes, problems, wrongs in order to implement corrections and set things right. Often we CAN focus on positive things - solutions, happiness and things improve rather drastically. Darkness is not opposite of light, it is just the absence of it.
