“In Shakespeare’s words, ‘There is nothing either good or bad, but thinking makes it so.’ What is more, suffering or negativity is often misperceived by the ego as pleasure because up to a point the ego strengthens itself through it.
For example, anger or resentment strengthen the ego enormously by increasing the sense of separateness, emphasizing the otherness of others and creating a seemingly unassailable fortresslike mental position of ‘rightness.’
If you were able to observe the physiological changes that take place inside your body when possessed by such negative states, how they adversely affect the functioning of the heart, the digestive and immune systems, and countless other bodily functions, it would become abundantly clear that such states are indeed pathological, are forms of suffering and not pleasure.”
A New Earth: Awakening to Your Life’s Purpose, Eckhart Tolle, p.110-111.