Why can the mind not be fixed permanently on the Lord?

You are taking a tablet for your cold (common cold) and are drinking ice-cold water throughout the day. The tablet can control the cold temporarily for an hour. But by the next day your cold will be back to the original state due to the cold water. What is the use of the medicine without following the restriction on the food and drinks (Pathyam)? Similarly you are taking divine knowledge in the discussions with the Sadguru but you are immediately entering into family affairs. By the time you come to the Sadguru, you are again in the original state. Therefore you must try for devotion (Bhakti) and also practice detachment from the family (Vairaagyam) simultaneously.