This is a lyrical masterpiece of devotion of Vishnu by Sri Yamunacharya, the predecessor of Sri Ramanuja. Sanskrit text, with English transliteration, translation and notes.
Discriminate within yourself between the real and the unreal. Have you not read the Vedanta? Even when you sleep, keep the sword of discrimination at the head of your bed, so that covetousness cannot approach you even in dream. Practicing such strength, renunciation will gradually come, and then you will see the portals of heaven are wide open to you.
-Swami Vivekananda