《COURAGE之言》There are two reasons when you want to teach something, one is expressing the success, the other is telling the failures.

There are two reasons when you want to teach something,
one is expressing the success, the other is telling the failures. 

-Translating from【Assassination Classroom】

In my opinion,
it is true,
when you want to talk something,
it might be share how difficult or how easy it is,
and give the experience.