Those who speak

Many years ago, when I was quite young, I gained a little bit of wisdom, which was:

To give advice when it is not requested is a waste of time.

It has taken me many years to realize the other side of this one, which is:

Listening to advice that you did not request is only of benefit to the ego of the advice giver.

'Those who speak do not know. Those who know do not speak.'
Indian proverb