Psalm 51:17 - If Our Prayers Do Not Change Us, Then We Do Not Pray Aright.

The sacrifices of God are a broken spirit: a broken and a
contrite heart, Psa 51:17 (KJV)

What pleases God more than sacrifices is a humble heart [NIV SB]

What really delights God is a heart that is open, humble, and
dependent upon God. [Jamieson, Fausset, And Brown Commentary]

God wants a broken spirit and a broken and contrite heart. You
can never please God by outward actions--no matter how good--if your
inward heart attitude is not right. Are you sorry for your sin? Do you
genuinely intend to stop? God is pleased by this kind of humility.  [Life
Application SB]

True repentance occurs when we begin to see sin from God's point
of view - when we see the way our sin has broken his heart.
Perhaps the idea that God's heart can be broken by our sin is new to
you.  In Gen.6:5-6 we are told, "Then the Lord saw that the
wickedness of man was great on the earth, and that every intent of the
thoughts of his heart was only evil continually.  And the Lord was sorry
that he had made man on the earth, and he was grieved in his heart"
(NASB).  God was so disappointed with what he saw that there was a grief
or sorrow in his heart.
Jesus also was brokenhearted as he wept over Jerusalem.  "O
Jerusalem, Jerusalem, you who kill the prophets and stone those sent to
you, how often I have longed to gather your children together, as a
hen gathers her chicks under her wings, but you were not willing!"
(Lk.13:34).  God's heart aches over our sin.  It alienates us from him and
from our fellow believers.
If we want to have victory over sin and turn our lives
wholeheartedly over to God, then we must see our sin from God's perspective.
No sermon on hell can ever change a person's heart like seeing the
grief sin has brought to the heart of the One who created us.  We must
ask God to show us what our sin does to him.  As we do this and
begin to understand his great love for us, despite how much we have
hurt and grieved his heart then we will want to turn away from sin
and let God give us new desires with new ways of living.  [Floyd
McClung; Time with God devotional SB mod]

New "miracle" products emerge all the time, loudly heralded for
their ability to clean everything from "tough, ground-in dirt" to
"ring-around-the-collar." But there is still one cleaning job
they are powerless to
accomplish: the cleansing of a dirty heart.
Psalm 51 was penned during the darkest hour of David's life. For
perhaps 20 years, the shepherd-king had ruled in righteous grandeur. But
overnight his sin with Bath-sheba changed all that. First adultery, then
murder inflicted ugly scars on the king's life. Nathan the prophet was
sent by God to confront David with the severity of his sin. And David
responded with a heartfelt prayer for forgiveness: "Wash me ... cleanse
me.... Create in me a clean heart" (w. 2,10).
David knew that forgiveness involves two parties: the offender
and the offended. Unless the offended party is willing to put away
the wrong that's been done, fellowship cannot be restored. The price
of pardon is never cheap, but David knew it must be paid. "The
sacrifices of God are a broken spirit: a broken and a contrite heart, O
God, thou wilt not despise" (v. 17).
Has your walk with God been interrupted by a dark stain of sin?
Then get up right now and find a place where you can wash your hands.
As you do, ask God to wash your heart as well. Confess your
specific offenses against God, and experience His cleansing--the kind no
soap can produce (1 John 1:9).
If our prayers do not change us, then we do not pray aright.
[Your Daily Walk SB]

Every act of transgression, every neglect or rejection of the
grace of Christ, is reacting upon yourself; it is hardening the heart,
depraving the will, benumbing the understanding, and not only making you
less inclined to yield, but less capable of yielding, to the tender
pleading of God's Holy Spirit. . . . Even one wrong trait of character,
one sinful desire, persistently cherished, will eventually
neutralize all the power of the gospel. SC23-36

Christ manifested a love that is incomprehensible; and as the
sinner beholds this love, it softens the heart, impresses the mind, and
inspires contrition in the soul. . . . Those to whom He has forgiven most
will love Him most, and will stand nearest to His throne to praise
Him for His great love and infinite sacrifice. It is when we most
fully comprehend the love of God that we best realize the sinfulness
of sin. When we see the length of the chain that was let down for
us, when we understand something of the infinite sacrifice that
Christ has made in our behalf, the heart is melted with tenderness and
contrition.  SC23-36

"The sacrifices of God are a broken spirit: a broken and a
contrite heart, O God, Thou wilt not despise." Ps. 51:17. Man must be
emptied of self before he can be, in the fullest sense, a believer in
Jesus. When self is renounced, then the Lord can make man a new
creature. New bottles can contain the new wine. The love of Christ will
animate the believer with new life. In him who looks unto the Author and
Finisher of our faith the character of Christ will be manifest. DA278-280