If you have learned much Torah, do not take credit for yourself (Ethics of the Fathers 2:9).
The Talmud does not hesitate to reveal shortcomings of great sages, so that we learn that we are all susceptible to err and that our greatest scholars accepted reprimand even from their inferiors and did teshuvah.
On returning from a successful term at the academy, Rabbi Eliezer ben Shimon allowed his ego to soar because of his great progress in learning. On the way, he encountered a man who was exceedingly ugly and said to him, "Are all the people in your city as ugly as you?" The man responded, "Why don't you go and complain to the One Who fashioned me?"
Rabbi Eliezer realized what a terrible thing he had said. He begged the man's forgiveness, but the latter refused. When they entered the town, and Rabbi Eliezer was greeted by the townsfolk, the man said to them, "He does not deserve to be called a rabbi." Only after the people pleaded with the man did he forgive Rabbi Eliezer, cautioning him never to allow his achievements to go to his head again.
How could Rabbi Eliezer have made such a gross remark? The Talmud cites this incident to tell us that vanity is so degenerating a trait that it can cause even a highly spiritual person like him to sink so low as to insult someone in this manner. Once a person feels superior to another, the arrogance that is likely to follow can bring in its wake the most vulgar attitudes.
We must be extremely cautious that we do not allow our successes to go to our heads.