Quote from A Course in Miracles Text Chapter 21 - REASON AND PERCEPTION.

T-21.VII.13. Elusive happiness, or happiness in changing form that shifts with time and place, is an illusion that has no meaning. 2 Happiness must be constant, because it is attained by giving up the wish for the inconstant. 3 Joy cannot be perceived except through constant vision. 4 And constant vision can be given only those who wish for constancy. 5 The power of the Son of God's desire remains the proof that he is wrong who sees himself as helpless. 6 Desire what you want, and you will look on it and think it real. 7 No thought but has the power to release or kill. 8 And none can leave the thinker's mind, or leave him unaffected.