Kakuan, a Chinese Zen master in the twelfth century drew the ten ox-herding pictures to describe the phases of Zen training:

For more commentary and the actual pictures, see Zen Flesh, Zen Bones and An Introduction to Zen Training.
After completely realizing one's true self (finding/herding the ox), one returns to the world to help all creatures. This stage transcends holiness -- in fact the enlightened person forgets about enlightenment.
At this ultimate stage of enlightenment, nobody, "even one thousand sages", can tell any longer whether he is a fool or a clever man, and whether he is sacred of profane. To such an extent has he lost his own identity, whether he is enlightened or unenlightened, good or bad, male or female. In addition, he has completely deprived himself of his beauty gained at any cost. It does not matter to him at all now, if others call him a lunatic or a traitor. He is, therefore, no longer bound to external laws in his freedom, and no longer arrested by any moral codes in his self-liberation. He is capable of acting freely at will in accordance with his varying opportunities and circumstances without necessarily restricting himself to the "good examples set by his wise predecessors."
Although I would not presume to have even seen the ox's droppings yet, I chose to tattoo the tenth ox herding image on my back as a reminder -- Sentient beings are numberless. I vow to save them all.. I first glimpsed then stepped on the Bodhisattva path a few years ago. They say once you start walking the path, you never leave it.
Now, if someone asks why I got that tattoo, I can repeat what I just wrote. Or, to save time, "I got it because it looks cool and stuff."