The Psalmist begins with self-control,
Psalm 39:1 (ESV)
1 I said, “I will guard my ways,
that I may not sin with my tongue;
I will guard my mouth with a muzzle,
so long as the wicked are in my presence.”
The reason is good, “that I may not sin with my tongue.” As Spurgeon writes,
I steadily resolved and registered a determination. In his great perplexity his greatest fear was lest he should sin; and, therefore, he cast about for the most likely method for avoiding it, and he determined to be silent. It is right excellent when a man can strengthen himself in a good course by the remembrance of a well and wisely-formed resolve.
C. H. Spurgeon, The Treasury of David: Psalms 27-57, vol. 2 (London; Edinburgh; New York: Marshall Brothers, n.d.), 214. Now, perhaps this was repression as opposed to a godly determination: self-will as opposed to godly blessing when cursed; because,
Psalm 39:2–3 (ESV)
2 I was mute and silent;
I held my peace to no avail,
and my distress grew worse.
3 My heart became hot within me.
As I mused, the fire burned;
then I spoke with my tongue:
This moves the Psalmist on to a prayer which will provide the basis for his transformed affection: to learn how brief one lives:
Psalm 39:5–6 (ESV)
5 Behold, you have made my days a few handbreadths,
and my lifetime is as nothing before you.
Surely all mankind stands as a mere breath! Selah
6 Surely a man goes about as a shadow!
Surely for nothing they are in turmoil;
man heaps up wealth and does not know who will gather!
How our responses to our circumstances do not match reality: “Surely for nothing they are in turmoil”. Our affections are judgments upon our circumstance: we think our anger justified, necessary because some tremendous has taken place. We think our lust for power meaningful, our wealth and fame: but, “man goes about as a shadow”.