It's Not Easy To Undo What's Done
It is easier to write on a clean slate
Watch a student getting an answer wrong and trying to erase it. He will adopt various ways to erase it and that will result in that portion of the paper getting creased or torn.
Undoing is always tough. It is easier to write on a clean slate. That is why even I find it tough to mould people and transform them for the better.
The loftier your thoughts, the further you progress in life. Do not be content with applying for the post of a manager and getting promoted. Seek to be God. Take whatever efforts required for that.