A Calm Spirit!

“He who has knowledge spares his words,
And a man of understanding is of a calm spirit.”
Proverbs 17:27 NKJV
 
Hmm!

 
What kind of knowledge and understanding is the above verse talking about?
 
“The fear of the Lord is the beginning of wisdom,
and knowledge of the Holy One is understanding.” Proverbs 9:10 ///