“I said, “I will guard my ways so that I may not sin with my tongue; I will guard my mouth with a muzzle as long as the wicked are in my presence.” I was speechless and quiet; I kept silent, even from speaking good, and my pain intensified. My heart grew hot within me; as I mused, a fire burned. I spoke with my tongue: “Lord , reveal to me the end of my life and the number of my days. Let me know how short-lived I am. You, indeed, have made my days short in length, and my life span as nothing in Your sight. Yes, every mortal man is only a vapor. Selah “Certainly, man walks about like a mere shadow. Indeed, they frantically rush around in vain, gathering possessions without knowing who will get them. Now, Lord, what do I wait for? My hope is in You. Deliver me from all my transgressions; do not make me the taunt of fools. I am speechless; I do not open my mouth because of what You have done.”

Psalms 39:1‭-‬9

King David wrote Psalm 39 and knew something about life that I’ve spent years finding out: MANY times the right thing to say is nothing at all! My dad always told me “if you don’t something nice to say, don’t say anything at all”. David’s assertion goes well past that-he contends that the best way for him not to sin was to keep his mouth shut. I can completely relate with this. Sometimes even “nice things” said in flattery, manipulation or trying to score influence with someone, leads to sin or situations we wind up wishing we could rebound from!
David had determined in whatever curcumstance he was in when he wrote this song, that he needed to keep quiet.
His psalm then moves to the fraility of human life. He uses such metaphors as a “mere vapor” or “shadow” to express the shortness of human life in the light of eternity. He asks God to teach him to “number his days”–in other words, to help him consider how short life, long lived really is, much less, cut short, and to live as if the end of life was near.
The coupling of these two subject was not a mistake.

Life is short. Too short to have to patch ruined relationships damaged by words said in anger or haste. Too short to have to out live even good things promised in haste. Too short to live wrecklessly.
James says that the person who can control their mouth, has control of everything else in their life. (James 3:2) Jesus called the man who presumed upon “tomorrow” or a “long life” a fool (Luke 12:20). Maybe in the sum of things words spoken hastely, whether good or bad and life lived wrecklessly, amount to foolishness, while good words, carefully chosen to speak into the recipient’s life and a life, lived well and in respect to eternity, amounts to wisdom.
If wisdom about how to speak and/or live life escapes us, God says we need simply to ASK for it! (James 1:5) Think about it!