At night, strive to invoke the self-purification of confused dreams.
Guard the three doors with the hook of mindfulness.
Retain, purify, increase and transform the content of dreams,
And eliminate all obstacles to practice.
One rides on the sun and moon, travels to all buddhafields,
And behold! All "good" and "bad" illusions become self-liberated.

Quoted from Vajra Verses of the Whispered Tradition by Naropa [1016-1100]. Published by Snow Lion (1997) in The Practice of the Six Yogas of Naropa, translated by Glenn H. Mullin.