The Drityigri Shaitaya is giving an optional back up. If this, the path of knowledge, culminating in Vedantic meditation is not working for you, then simply sit and try to focus with a firm resolve. Use the process of repetition. You can concentrate on a mantra or something. Focus the mind into a stage of state of steadiness.
Swami Sarvapriyananda teaches Chapter 6 (Verses 26-27) of the Bhagavad Gita. In this series of talks, Swami Sarvapriyananda unfolds the highest truths of Vedanta through the study of the Bhagavad Gita (The Song of God).