"The mind is its own place and in itself can make a hell of heaven or a heaven of hell"
—Milton, Paradise Lost
You are what you think. Whatever you are doing, whatever you feel, whatever you want—all are determined by the quality of your thinking. If your thinking is unrealistic, your thinking will lead to many disappointments. If your thinking is overly pessimistic, it will deny you due recognition of the many things in which you should properly rejoice.
Test this idea for yourself. Identify some examples of your strongest feelings or emotions. Then identify the thinking that is correlated with those examples. For example, if you feel excited about going to work, it is because you think that positive things will happen to you while ...