The old man asked the Saint, “O Sadhu Maharaj! Why did you not advise the boy on the first day?” The Saint replied: “I was myself a victim of the sugar-eating habit. How could I then be able to advise others? I gave it up for fifteen days. I corrected myself first. How can I preach to others when I am myself filled with Doshas?” The advice of the Saint had very great effect on the mind of the boy. He gave up eating sugar from that day.
The moral of this story is that you must put a thing into actual practise yourself before you begin to preach. Then only it to others. will it produce a lasting impression. Example is better than precept. It is easier to preach to twenty than to be one of the twenty in following the preaching.
(pgs. 129-130, Yoga in Daily Life)