To consume yourself does not mean to destroy yourself but to work and improve yourself. The 'job' of a candle is to consume itself, in other words to work for others. Your job as a teacher is to keep ''the light of the candle lit'' as much as possible, as long as possible. And the best way to develope our knowledge, our vocabulary, our language skills ( reading, listening, writing, speaking ) is to teach others. Since by teaching others you also teach yourself. When you teach, in fact, you revise/repete the subject matter. REPETITION IS THE MOTHER OF SKILL! A good teacher must devote him/herself to his/her job entirely.