Proverbs 10:19

When words are many, transgression is not lacking,
but whoever restrains his lips is prudent.
We have a similar saying: Give a man enough rope and he will hang himself. The more verbose we are the more likely we will say something to get ourselves in trouble or cause trouble.
The reason is simple. We are sinners. Sin is always looking for an outlet and the mouth provides a wide open one. We speak inappropriate words. We speak words, that in themselves are fine, but our tone of voice is inappropriate. We speak at inappropriate times.

Thus, the prudent person is the one who literally speaks less words. He waits for others to speak before throwing out his opinion. He gives thought to what he says, and that very exercise of thinking before speaking leads to less words.
Better to regret not knowing what to have said than to regret what was said. Better to leave others wishing you had spoken than to wish you had not.