To think correctly, scientifically, we must know the "Truth." To know the truth is to be in harmony with the infinite intelligence and power of your subconscious mind, which is always moving lifeward.
Every thought or action, which is not harmonious, whether through ignorance or design, will result in discord and limitation of all kinds.
You are the sum total of your own thoughts. You can keep from entertaining negative thought and imagery. The way to get rid of darkness is with light; the way to overcome cold is with heat; the way to overcome the negative thought is to substitute the good thought. Affirm the good, and the bad will vanish.