As for me, etc. Literally, it is, And I: which ought to be read with emphasis; for David means that those temptations, which cast an affront upon the honor of God, and overwhelm faith, not only assail the common class of men, or those who are endued only with some small measure of the fear of God, but that he himself, who ought to have profited above all others in the school of God, had experienced his own share of them. By thus setting himself forth as an example, he designed the more effectually to arouse and incite us to take great heed to ourselves. He did not, it is true, actually succumb under the temptation; but, in declaring that his feet were almost gone, and that his steps had well nigh slipped, he warns us that all are in danger of falling, unless they are upheld by the powerful hand of God.

But as for me - literally, "And I." The meaning is, "And I, who so confidently now trust in God, and believe that he is good, was formerly in a far different state of mind; I was so hesitating, so troubled, and so doubtful, that I had almost entirely lost confidence in him as a wise and just moral governor."
My feet were almost gone - I was just ready to fall. Of course, this refers to his state of mind. In regard to his faith or confidence in God, he was like a man standing in a slippery place, and scarcely able to remain upright.
My steps had well nigh slipped - The expression rendered "well nigh" means "like nothing," or "as nothing;" that is, in reference to firmness it was as if there was "nothing" left. There was nothing which would keep him from slipping. The word rendered "slipped" means "poured out." That is, in his going he was like water poured out, instead of being like something solid and firm. The idea is, that his faith seemed to be all gone. He was like a falling man; a man who had no strength to walk.

My feet were almost gone - I had nearly given up my confidence. I was ready to find fault with the dispensations of providence; and thought the Judge of all the earth did not do right.

But as for me,.... Who am one of the Israel of God whose heart has been renewed and purified by the grace of God, and to whom he has been kind and good in a thousand instances; yet, ungrateful creature that I am,
my feet were almost gone; out of the good ways of God, the ways of truth and holiness just upon the turn, ready to forsake them, and give up all religion as a vain thing:
my steps had well nigh slipped, or "poured out" (c) like water; the allusion is to standing on wet and slippery ground, where a man can scarcely keep upon his feet. It may be observed, that good men are liable to slips and falls, to fall into sin, snares, and temptations, and from their steadfastness in the faith, but not totally and finally; their feet may be "almost", but not "altogether", gone: their steps may "well nigh" slip, but not "quite"; they may fall, but not be utterly cast down; at least they rise again, and are made to stand; for God is able to keep them, and does keep them, from a total and final falling away.
(c) "effusi sunt", V. L. Pagninus, Montanus, Cocceius; "effusi fuissent", Musculus, Gejerus, Michaelis.

The figures express his wavering faith, by terms denoting tottering and weakness (compare Psalm 22:5; Psalm 62:3).

My feet - My faith in God's providence, was almost overthrown.