A recent study at HuffPost-UK titled, "Happiness Is The Key To A Longer Life," stated the following, "Feeling happy and having a positive outlook on life could be the key to a longer life.....The five year study of almost 4,000 people aged between 52 and 79 years old, discovered that those who were happier and more content had a lower risk of dying young than those who looked on the gloomier side of life. Optimism is good for you, which makes sense. ("Researchers took into account age, disease, health related conditions and gender before coming to their conclusions.") This information reinforced a previous study at the University of Illinois which found that positive thinking reduced stress and made the immune system stronger.
I use positive affirmations, at times, to feel better as I tend to worry which is obviously not good for my health. Positive affirmations from Scripture such as, "With God all things are possible," or "God is my rock and my salvation in whom I trust," helps to lift my spirits. I also like to repeat, "I am a child of God, a member of the household of God, made in the image and likeness of God." Or "I can do all things through Christ who strengthens me," is another powerful quote from Scripture, which is helpful for keeping a positive outlook.
Christian meditation also helps one to put things into perspective, but it takes discipline to do it everyday (in addition to my prayer disciplines) and it takes time to see the "fruit" of doing it.
I have to work at staying positive, even with my deep faith and trust in God. Every life is a work in progress, but it seems staying positive has many health benefits.