I once heard the following explanation:
In Parshas Beha'aloscha (Bamidbar 8:3), after Aahron Hakohen was tasked with lighting the Menorah, the Torah tells us that "ויעש כן אהרן" - Aaron did so. Rashi there cites the Sifrei (1:5) that it was necessary for the Torah to advise us that Aahron in fact complied with the Divine instruction, for "this shows Aaron’s virtue that he did not deviate [from God’s command]". Many question why the mere fact that Aaron obeyed Hashem's command here is deemed so praiseworthy.
Rabbi Levi Yitzchok of Berdichev explained as follows: For any ordinary person, fulfilling G-d's instruction would be nothing notable. However, for someone on the calibre of Aahron, who understood what was going on "behind the scenes", this was truly an exceptional achievement. Aaron was aware that the seven branches of the Menorah represented the seven different types of Middos (character traits) present in each Jewish soul, and his lighting of each candle affected the igniting of the Jewish souls. When faced with such a level of comprehension and appreciation of the task at hand, many would be so "blown away" that they could not perform the job satisfactorily; they would become so excited that they would spill the oil everywhere and not manage to light the candles. The greatness of Aahron was that in spite of his high level, he was still able to perform the job as required.
I've heard people bringing this as an explanation to what happens to many "Chassidic tales". The Chassidim are so excited by the greatness they perceive of their Rebbeim, that their stories "grow hands and feet". There is no malicious intent of course, but they are simply unable to contain themselves to “stick to the facts”. (But as a lawyer once said to the Judge when introducing the Chofetz Chaim to the witness stand: “Whether the stories they say about him are true or not is irrelevant. The point is that they don’t tell these stories about me and you!”)