( Story told by Swami Vivekananda )
The whole of the Vedanta Philosophy is in this story: Two birds of golden plumage sat on the same tree. The one above, serene, majestic, immersed in his own glory; the one below restless and eating the fruits of the tree, now sweet, now bitter. Once he ate an exceptionally bitter fruit, then he paused and looked up at the majestic bird above; but he soon forgot about the other bird and went on eating the fruits of the tree as before. Again he ate a bitter fruit, and this time he hopped up a few boughs nearer to the bird at the top.
This happened many times until at last the lower bird came to the place of the upper bird and lost himself. He found all at once that there had never been two birds, but that he was all the time that upper bird, serene, majestic, and immersed in his own glory.
Source: The Complete Works of Swami Vivekananda/Volume 7/Inspired Talks/Tuesday, July 30