A teacher's joy comes when the student has a spark of understanding in his eyes. A teacher's pain comes when the student ignores everything that took effort to impart. A teacher's frustration comes when students cannot reach their potential. A teacher's despair comes when gifted students have big egos, and the non gifted continue to deny the obvious about themselves.
A teacher is a fragile creature, whose well being is often influenced by the students he nurtures. But the student is always oblivious to the impression he leaves behind.