"Create in me a clean heart, O God, and renew a right spirit within me" (Psalm 51:10)
None of us can really tell how weak and useless we are until God has exposed us - and no one wants to be exposed! But God knows so much better than we do that He must expose us for our own good.
Neither do any of us really know how unstable we are until we have been exposed by the Holy Spirit. Peter was a big, bold, strong fisherman, and it seemed easy for him to say to the Lord, "Let everyone else run away, but I will always stand by. You can count on me, Master!" I am sure it was hard for him to take the answer that Jesus gave him: "Before the rooster crows tonight you will say three times that you do not know me!" (Matthew 26:33-34). But Jesus knew the instability of the man who still tried to stand in his own strength and in his own self-trust.
We do not really know how unstable we are, and we often refuse to admit the truth when we find out, when we are exposed. That is why it is too dangerous to trust our good habits and our virtues - and that is why our distrust of ourselves must be the work of God's hand.
We must pass sentence upon our sinful heart and give God the right to cleanse it.
~A. W. Tozer~