There is no greater insult to a teacher than to forever remain a student.

People who devote their lives to Nietzche's work irritate me. Those people also irritate Zarathustra, who writes: "One requites a teacher badly if one remains merely a student."

If I remember correctly, the Kaufmann edition is slightly different, with Zarathustra saying, "There is no greater insult to a teacher than to forever remain a student."

Regardless of the preferred translation, the morale is clear.