No matter what image we hold in our mind, the body will secrete chemicals to manifest the feeling of the image. When we react to a situation, we are, in actuality, re-acting previous responses. This is enlightenment. Here we learn to find bliss in all of life's situations. This may sound difficult, but actually it is much more difficult to NOT practice this way of responding to life's situations.
Negative responses use much energy and are non-productive.
A positive mind is a mind clear to options that are overlooked when a negative state of mind is prevalent. First of all, you must have total faith in God to the point that you feel good about creating positive thought in spite of all outside influences that dictate the notion of negative thought. To have this faith you must rationalize that all negative thought will harm you or others and all divine positive thought will parallel the will of God. I have had a few people argue that they would feel foolish having blind faith to the point that they would create positive thoughts when things are in chaos or in moments of serious misfortune. I can only retaliate by saying that using negative thought in any situation will always seriously inhibit our potential to handle any situation and that negative thought usually causes us to justify doing something foolish or worse.