One of the great Sages of the 20th century, Rabbi Yeruchem Levovitz, observed: "People become so used to being unhappy that they are unaware of the needless misery they cause themselves. They imprison themselves by filling their minds with thoughts of resentment, hatred, and envy. It is amazing how they tolerate living such a life. The only reason they do tolerate it is because they have become so used to living with these thoughts that they feel it's normal. They think it's impossible for life to be any different!"
Be totally resolved to free your mind from thoughts of resentment, hatred, and envy. If your brain focuses on thoughts that needlessly cause you emotional distress, say a loud, "NEXT!" Then begin to focus on something else that will be more worthwhile. You have the ability to make yourself happy!
(see Gateway to Happiness, p.24)