Therefore, let him who thinks he stands take heed lest he fall. – 1 Corinthians 10:12

Examine yourselves as to whether you are in the faith. – 2 Corinthians 13:5

One thought may occur to the most joyous believer. He will say, “What if after rejoicing in all this blessedness I should lose it?” “What,” cries one, “do you not believe in the final perseverance of the saints?” Assuredly I do, but are we saints? There’s the question. Moreover, many a believer who has not lost his soul has, nevertheless, lost his present joy and prosperity, and why may not we? The good man has shone as a star of the first magnitude, but suddenly he has dwindled into darkness: he has been unwatchful, and in consequence by the dozen years together he has had to go softly in the bitterness of his soul. We have known fathers in Israel who have stepped aside, and though they have by deep repentance found their way to heaven, they have gone sorrowing thither. Look at David’s history. Note that one sin with Bathsheba, and ask who was more tried and troubled than David throughout the rest of his pilgrimage? The doctrine of final perseverance was never intended for the comfort of any who are afraid of self-examination, or who are not watchful; for it is by no means at variance with the other doctrine that many who made sure of heaven in their own minds will never enter there, because Jesus never knew them. Great joy may be only a meteor, great excitement may be a mirage of the desert, great confidence may be a will-o’-the-wisp luring to destruction. The highest seats in the synagogue do not secure for their occupants a place among the shilling ones above. Many rejoicing professors will yet discover that their spot was not the spot of God’s people, and their song was not the new song which God doth put into the mouth. And what if that should be your case and mine? So, when I stand upon my high mountain, let me pray, “Lord, hold thou me up.” Let him that thinketh he standeth take heed lest he fall, for he is the man who is most in danger. He who is fullest of holy delight is still to watch, for did not Jesus say, “What I say unto you I say unto all, watch”? God grant that we may be helped to watch against the arrow which flieth by day as much as against the pestilence which walketh in darkness. ~ C.H. Spurgeon

https://www.spurgeon.org/resource-library/sermons/chastened-happiness/#flipbook/