Answer:
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
You should keep it as straight as can be, yet very few do. Most of the time it's slightly bent or curved. Your sadness usually causes it to bend further, but donβt bend it for too long or it may never be able to fully straighten out again. What is it?
What can be filled with empty hands?
I never was but always will be. No one ever saw me but everyone knows I exist. I give people the motivation to better themselves every day. What am I?
What word starts with 'E', ends with 'E', but only has one letter? It is not the letter 'E'.
My days are numbered. What am I?