Rav Yaakov Galinsky ztz"l [who passed away recently at close to 100 years of age] related the following story that he heard from old Chabad chasidim .
There was once a weding where the badchan was saying words of rebuke to those present. The Baal Hatanya [Rav Schneur Zalman of Liadi] asked him for some rebuke as well. The badchen said that he can't for he is afraid. The Baal Hatnya told him not to worry and to proceed.
He said as follows: "What is the difference between you and I? What you don't know - I also don't know. What I know - you also know. What then is the difference? You know things that I don't know. But what is that compared to what we both don't know...."
The Baal Hatanya cried when he heard these words and he realized how far he is from knowing all of Hashem's Holy Torah which is endless.