I chanced upon a beautiful commentary on tanha by Eknath Easwaran in his translation of The Dhammapada (he uses the Sanskrit equivalent of tanha, "trishna"):
In Buddhist psychology, each desire is an isolated moment of mental activity - a dharma, in the Buddhist technical vocabulary - rising up in the mind. It can be ignored, or one can choose to yield to it. If one yields, the next wave of desire will have greater power to compel attention, and the mental agitation it causes will be more intense. On the other hand, if one chooses to defy a strong desire, the pain can be considerable. “Know me to be the power called Thirst,” Trishna demands of the Buddha on the eve of his enlightenment, “and give me my due of worship. Otherwise I will squeeze you with all my might and wring out the last of your life!” However, if one succeeds in not giving in to selfish desires as they arise, the mind gradually quiets down, leaving a longer and longer interval between waves of desire in which the mind is calm. This calmness is our natural birthright, a state beyond the suffering entangled with desire. All the Buddha’s teachings come round to this one practical point: to find permanent joy, we have to learn how not to yield to selfish desire.
(** It get worse. Apparently, the Chinese translation for tanha is 愛, which literally means "love". Whoever made THAT translation deserves to be slapped.)