The greater part of human pain is unnecessary. It is self-created as long as the unobserved mind runs your life. The pain that you create now is always some form of non-acceptance, some form of unconscious resistance to what is. On the level of thought, the resistance is some form of judgment. On the emotional level, it is some form of negativity. The intensity of the pain depends on the degree of resistance to the present moment, and this in turn depends on how strongly you are identified with your mind. The mind always seeks to deny the Now and to escape from it.
In other words, the more you are identified with your mind, the more you suffer.
Excerpt from book ‘The Power of Now’ By Eckhart Tolle