“At present most of the happy feelings that increase our attachment are minds of happiness that arise with respect to a relief of suffering. Yet there is no happiness by way of its own entity that is unrelated to suffering. For instance, if you suffer because you have walked too much, the mind of happiness that arises due to sitting down appears to be happiness that arises gradually while the great previous suffering gradually ceases. However, it is not happiness by way of its own entity, for if you sit too much, again, that will produce suffering as before. If they were causes of happiness by way of their own entity, just as suffering increases to the same extent as you are subject to the causes of suffering, so too should walking, sitting, lying, eating and drinking, as well as sun and shade, and the like increase your happiness to the same extent that you indulge in them. However, it appears that in the long term only more suffering is produced.”
From The Medium Treatise on the Stages of the Path to Enlightenment by Je Tsong Khapa
As translated in: Middle Length Lam-Rim with Trijang Rinpoche’s Additional Outlines by Lama Tsongkhapa (and Trijang Rinpoche). Translated by Philip Quarcoo. Unpublished DRAFT translation (May 2012) by FPMT, Inc. Download the PDF here.