By associating ourselves with our mind, which houses our ego, we become defined by our emotions. We begin to resist the now because the ego cannot coexist with the present. The ego is fueled by the past and the future, as our survival depends on past experiences and future planning. Our false sense of self, created by the ego latching onto our conscious mind, cannot thrive without dualities such as pain and pleasure, two sides of the same coin.
It is only by observing our mind from an external perspective that we can be truly present. Otherwise, we become defined by our minds, which is a culmination of the pain-body, past failures, and future uncertainties. The ego wants to maintain its hold, and if we are defined by it then we cannot let go of pain. The ego is afraid of losing pain, because it is afraid of losing a hold you, a false sense of identity. Instead the ego holds onto pain and seeks external pleasures to temporarily distract you from pain. Maintaining this vicious cycle becomes increasingly difficult, as pleasure fuels the pain which fuels the need for pleasure.
Eventually you will break and seek true happiness, a detachment from and deterioration of the false sense of self created by the ego. Only then will you be in touch with your true self, the pinnacle of unconditional love, inner peace, and eternal joy.