Sin is what you do when your heart is not satisfied with God. No one sins out of duty. We sin because it holds out some promise of happiness. That promise enslaves us until we believe that God is more to be desired than life itself (Psalm 63:3). Which means that the power of sin's promise is broken by the power of God's.
John PiperHusbands and wives, recognize that in marriage you have become one flesh. If you live for your private pleasure at the expense of your spouse, you are living against yourself and destroying your joy. But if you devote yourself with all your heart to the holy joy of your spouse, you will also be living for your joy and making a marriage after the image of Christ and His church.
John PiperWhenever your heart starts to be anxious about the future, preach to your heart and say, 'Heart, who do you think you are to be afraid of the future and nullify the promise of God? No, heart, I will not exalt myself with anxiety. I will humble myself in peace and joy as I trust this precious and great promise of God - He cares for me.'
John PiperEvery Christian who struggles with depression struggles to keep their hope clear. There is nothing wrong with the object of their hope - Jesus Christ is not defective in any way whatsoever. But the view from the struggling Christian's heart of their objective hope could be obscured by disease and pain, the pressures of life, and by Satanic fiery darts shot against them... All discouragement and depression is related to the obscuring of our hope, and we need to get those clouds out of the way and fight like crazy to see clearly how precious Christ is.
John PiperPeople are not prepared or able to rejoice in suffering unless they experience a massive biblical revolution of how they think and feel about the meaning of life. Human nature and American culture make it impossible to rejoice in suffering. This is a miracle in the human soul wrought by God through His Word.
John Piper