Lately I have been reading "Vivekananda - A Biography" by Swami Nikhilananda. It's a really good book, and if you are interested in knowing about the great yogi and sannyasin Swami Vivekananda and how he did a lot to bring eastern thinking and vedanta to America, this is the book for you.
I especially like this quote from the book which is a story about an event that happened with Swami Vivekananda and which I think demonstrates the detachment of a true sannyasin's mind:
"He [Swami Vivekananda] was one day walking with Miss Muller [a student] and an English friend across some fields when a mad bull came tearing towards them. The Englishman frankly ran, and reached the other side of the hill in safety. Miss Muller ran as far as she could, and then sank
to the ground, incapable of further effort. Seeing this, and unable to aid her, the Swami - thinking, "So this is the end, after all" - took up his stand in front of her, with folded arms.
"He told afterwards how his mind was occupied with a mathematical calculation as to how far the bull would be able to throw him. But the animal suddenly stopped a few paces off, and then, raising its head, retreatedsullenly. The Englishman felt ashamed of his cowardly retreat and having left the Swami alone to face the bull. Miss Muller asked the Swami how he could muster such courage in such a dangerous situation. He said that in the face of danger and death he felt - and he took two pebbles in his hands and struck the one against the other - as strong as flint, for "I have touched the feet of God."