A lot of the behavioural problems and troubles adult face later on in their life did not suddenly start overnight. It started from very little issues overlooked and excused, then over time the accumulated ripple effects becomes overwhelmingly worrisome.
It is easier and faster to correct and adjust a child's behaviour at an early stage in their life. "Train up a child in the way he should go so that when he grows he will not depart from it."
(Proverbs 22:6)