Not of works, lest any man should boast. – Ephesians 2:9

Have not you sometimes found, that when you thought you were standing on a rock, there was a quivering beneath your feet? You heard the Christian sing boldly:

“Bold shall I stand in that great day,
For who aught to my charge shall lay?
While, thro’ Thy blood, absolv’d I am
From sin’s tremendous curse and shame.”

And you have said, “Well, I cannot sing that, I have been as good a Churchman as ever lived, I never missed going to my church all these years, but I cannot say I have a solid confidence.” “Well,” says another, “I have been to my chapel, and I have been baptized, and made a profession of religion, though I was never brought to know the Lord in sincerity and in truth, and I once thought it was all well with me, but I want a something which I cannot find.” Now comes a shaking in the heart. It is not quite so delightful as one supposed, to build on one’s own righteousness. How many a man who has been self-righteous all his life, has, at the last discovered that the thing whereon he placed his hope had failed him…You thought there was a bridge of ceremonies; that baptism, confirmation, and the Lord’s Supper, made up the solid arches of a bridge of good works and duties. But when you come to die, there shall be heard the cry-“The bridge is broken, the bridge is broken!” It will be in vain for you to turn round then. Death is close behind you; he forces you onward, and you discover what it is to perish through having neglected the great salvation and attempting to save yourself through your own good works. Good as you thought yourself to be, inasmuch as you proudly rejected Christ, you must drink the winecup of the wrath of God; that cup which is full of trembling. The wicked of the earth shall wring out the dregs of that cup, and drink them; and you also must drink of it as deep as they. Oh, beware in time! Put away your high looks, and humble yourselves under the mighty hand of God. Believe on the Lord Jesus Christ and ye shall be saved. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0225.cfm