Why nagging does not work
We're all familiar with some form of nagging. The common form would be the nagging associated with our well-meaning parents.
The dictionary defines nagging as "constant harassing someone to do something."
Wow, to think that loving parents would harass their children just doesn't compute.
Children don't take well to nagging even though they may inwardly acknowledge it is for their own good.
Why nagging is ineffective is because it sometimes makes people angry.
It is not directly forcing a person but it is like finding fault with someone over and over.
What happens is that resentment will build over time.
At that point, whatever you say or do will not promote a healthy outcome in whoever's behaviour you wished to change in the first place.