Charles H. Spurgeon on Psalms 119:28

My soul melteth for heaviness. He was dissolving away in tears. The solid strength of his constitution was turning to liquid as if molten by the furnace heat of his afflictions. Heaviness of heart is a killing thing, and when it abounds it threatens to turn life into a long death, in which a man seems to drop away in a perpetual drip of grief. Tears are the distillation of the heart; when a man weeps he wastes away his soul. Some of us know what great heaviness means, for we have been brought under its power again and again, and often have we felt ourselves to be poured out like water, and near to being like water spilt upon the ground, never again to be gathered up. There is one good point in this downcast state, for it is better to be melted with grief than to be hardened by impenitence.

Strengthen thou me according unto thy word. He had found out an ancient promise that the saints shall be strengthened, and here he pleads it. His hope in his state of depression lies not in himself, but in his God; if he may be strengthened from on high he will yet shake off his heaviness and rise to joy again. Observe how he pleads the promise of the word, and asks for nothing more than to be dealt with after the recorded manner of the Lord of mercy. Had not Hannah sung, "He shall give strength unto his King, and exalt the horn of his anointed"? God strengthens us by infusing grace through his word: the word which creates can certainly sustain. Grace can enable us to bear the constant fret of an abiding sorrow, it can repair the decay caused by the perpetual tear drip, and give to the believer the garment of praise for the spirit of heaviness. Let us always resort to prayer in our desponding times, for it is the surest and shortest way out of the depths. In that prayer let us plead nothing but the word of God; for there is no plea like a promise, no argument like a word from our covenant God.

Note how David records his inner soul life. In Psalms 119:20 he says, "My soul breaketh; "in Psalms 119:25, "My soul cleaveth to the dust; "and here, "My soul melteth." Further on, in Psalms 119:81, he cries, "My soul fainteth; "in Psalms 119:109, "My soul is continually in my hand; "in Psalms 119:167, "My soul hath kept thy testimonies; " and lastly, in Psalms 119:175, "Let my soul live." Some people do not even know that they have a soul, and here is David all soul. What a difference there is between the spiritually living and the spiritually dead.