David asks the question in Psalm 19:12
12 Who can understand his errors?
Cleanse me from secret faults.
No one can understand their errors. Left to ourselves we will never fully discern the intentions and motives of our heart, and therefore never fully identify error within us.
The verse talks of secret faults. Faults that are secret even to us, that we are blind to, cannot see. Some times the shades between good and evil within us are too subtle for us to distinguish.
So if there’s all this bad stuff going on within us that we can’t identify, what’s the answer in terms of helping ourselves sort ourselves out?
The answer is given in the previous 5 verses of this Psalm, that sing the praises and virtues of God’s Word. Nothing will bring the truth about our own hearts more clearly into focus than God’s Word will.
Hebrews 4:12 tells us, it is sharper than any two edged sword and therefore the most effective instrument to cut, to define the boundary made at times by the very fine lines within our own hearts between good and evil.
Hebrews 4:12 goes on to say, it pierces even to the division of soul and spirit. As believers God’s Spirit is joined to our spirit, so the implication of this is that the Word Of God divides between what is of God in us and what is not. Like a surgeon’s scalpel blade it will accurately cut out all the bad, and preserve, leave behind all the good and healthy.
It is only with the help of God’s Word we’ll understand our errors and uncover our secret faults.