Since it is the nature of every evil to destroy itself along with the habits which brought it into being, man finds by experience that every pleasure is inevitably succeeded by pain, and so directs his whole effort towards pleasure and does all he can to avoid pain. He struggles with all his might to attain pleasure and he fights against pain with immense zeal. By doing this he hopes to keep the two apart from each other–which is impossible–and to indulge his self-love in ways which bring only pleasure and are entirely free from pain. Dominated by the passion of self-love he is, it appears, ignorant that pleasure can never exist without pain. For pain is intertwined with pleasure, even though this seems to escape the notice of those who suffer it.
~St Maximos the Confessor
Prayerful Life 