It is said by the masters that even a little poison can cause death, and even a tiny seed can become a huge tree. And as Buddha said: "Do not overlook negative actions merely because they are small; however small a spark may be, it can burn down a haystack as big as a mountain." Similarly he said, "Do not overlook tiny good actions, thinking they are of no benefit; even tiny drops of water in the end will fill a huge vessel."
— Sogyal Rinpoche, The Tibetan Book of Living and Dying by Sogyal Rinpoche, Patrick Gaffney, editor, Andrew Harvey,editor