“The way to cultivate love is as follows. Just as you can develop compassion once you have repeatedly thought about how living beings are made miserable by suffering, develop love by thinking repeatedly about how living beings lack all happiness, both contaminated and uncontaminated. When you become familiar with this, you will naturally wish for beings to be happy. In addition, bring to mind various forms of happiness and then offer them to living beings.”
From The Great Treatise on the Stages of the Path to Enlightenment by Je Tsong Khapa As translated in: The Great Treatise on the Stages of the Path to Enlightenment: The Lam Rim Chen Mo by Tsong Khapa. Translated by the Lamrim Chenmo Translation Committee. Snow Lion/Shambhala Publications.