"David's Prayer in the Cave"
https://www.spurgeon.org/resource-library/sermons/davids-prayer-in-the-cave/#flipbook/
Commentary in The Treasury of David
https://www.blueletterbible.org/Comm/spurgeon_charles/tod/ps142.cfm
v. 2
We do not show our trouble before the Lord that he may see it, but that we may see him. It is for our relief, and not for his information that we make plain statements concerning our woes: it does us much good to set out our sorrow in order, for much of it vanishes in the process, like a ghost which will not abide the light of day; and the rest loses much of its terror, because the veil of mystery is removed by a clear and deliberate stating of the trying facts. Pour out your thoughts and you will see what they are; show your trouble and the extent of it will be known to you: let all be done before the Lord, for in comparison with his great majesty of love the trouble will seem to be as nothing.
John Calvin
To pour out one's thoughts and tell over his afflictions implies the reverse of those perplexing anxieties which men brood over inwardly to their own distress, and by which they torture themselves, and are chafed by their afflictions rather than led to God; or it implies the reverse of those frantic exclamations to which others give utterance who find no comfort in the superintending providence and care of God. In short, we are left to infer that while he did not give way before men to loud and senseless lamentations, neither did he suffer himself to be tormented with inward and suppressed cares, but made known his grief's with unsuspecting confidence to the Lord.
Matthew Henry
I showed before him my trouble, and all the circumstances of it. He did not prescribe to God, nor show him his trouble, as if God did not know it without his showing; but as one that put a confidence in God, desired to keep up communion with him, and was willing to refer himself entirely to him, he unbosomed himself to him, humbly laid the matter before him, and then cheerfully left it with him. We are apt to show our trouble too much to ourselves, aggravating it, and poring upon it, which does us no service, whereas by showing it to God we might cast the care upon him who careth for us, and thereby ease ourselves. Nor should we allow of any complaint to ourselves or others which we cannot with due decency and sincerity of devotion make to God, and stand to before him.
Barnes' Notes
I poured out my complaint before him - literally, my meditation; that is, What so much occupied my thoughts at the time I expressed aloud. The word "complaint" does not express the idea. The meaning is, not that he "complained" of God or of man; but that his mind "meditated" on his condition. He was full of care and of anxiety; and he went and poured this out freely before God. The Septuagint and the Latin Vulgate render this, "my prayer." See Psalms 55:1-2, where the same Hebrew word is used.
God knows our troubles; God knows our fear and anxiety; God knows our pain.
If we can't verbalize our "complaint/lament/meditation", we don't really understand our "complaint". By sharing (and it is helpful to do so audibly) our thoughts with the Lord, we clarify (illuminate by the help of the Holy Spirit) the true source and nature of our "complaint"; then can turn it over to our Father in confidence and faith.
Psalm 62:8
Trust in Him at all times, O people; pour out your hearts before Him.