The Buddha always told his disciples not to waste their time and energy in metaphysical speculation. Whenever he was asked a metaphysical question, he remained silent. Instead, he directed his disciples toward practical efforts. Questioned one day about the problem of the infinity of the world, the Buddha said, "Whether the world is finite or infinite, limited or unlimited, the problem of your liberation remains the same." Another time he said, "Suppose a man is struck by a poisoned arrow and the doctor wishes to take out the arrow immediately. Suppose the man does not want the arrow removed until he knows who shot it, his age, his parents, and why he shot it. What would happen? If he were to wait until all these questions have been answered, the man might die first." Life is so short. It must not be spent in endless metaphysical speculation that does not bring us any closer to the truth.

~Thich Nhat Hanh, in Zen Keys 

From Tricycle magazines Daily Dharma 

Devotion, scholarship, and meditation can all be empty rituals, and whether these devotional acts or any other practices are in fact Dharma depends solely upon one's motivation. . . . Our initial attempts at spiritual practice tend to be very self-conscious. We want to overcome the distortions of our minds and cultivate such wholesome qualities as kindness, insight, mindfulness, and concentration; but as we engage in practices designed to cultivate these, at first they appear to be only mental exercises. Dharma seems separate, something adopted from outside. But as we go deeper into the practice, this sense of separation begins to disappear; our minds become the very Dharma we seek to cultivate.
~B. Alan Wallace, Tibetan Buddhism from the Ground Up

From Tricycle's Daily Dharma