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.
Take up one idea. Make that one idea your life -- think of it, dream of it, live on that idea. Let the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is the way to success, and this is the way great spiritual giants are produced. Others are mere talking machines.
-Swami Vivekananda