Atisha’s response to his parents’ proposal as documented in Buddhist biographical texts evidences the level of commitment the young prince had for religious pursuit and enlightenment. On the eve of his wedding, Atisha experienced a momentous encounter with the Vajrayana goddess Tara, who would continue with him as a guiding spirit until the end of his life. Tara explained to the prince that in his past lives he had been a devout monk. Wikipedia
The definitive Wikipedia entry for Atisha. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Atisha