Perhaps you can see why it is astonishing to me that so many people try to define true Christianity in terms of decisions and not affections. Not that decisions are unessential. The problem is that they require so little transformation. Mere decisions are no sure evidence of a true work of grace in the heart. People can make “decisions” about the truth of God while their hearts are far from Him.
We have moved far away from the biblical Christianity of Jonathan Edwards. He pointed to 1 Peter 1:8 and argued that “true religion, in great part, consists in the affections.”18
Though you have not seen Him, you love Him, and though you do not see Him now, but believe in Him, you greatly rejoice with joy inexpressible and full of glory. (1 Peter 1:8)
Throughout Scripture we are commanded to feel, not just to think or decide. We are commanded to experience dozens of emotions, not just to perform acts of willpower.
For example, God commands us not to covet (Exodus 20:17), and it is obvious that every commandment not to have a certain feeling is also a commandment to have a certain feeling. The opposite of covetousness is contentment, and this is exactly what we are commanded to experience in Hebrews 13:5: “Be content with what you have” (RSV).
God commands us to bear no grudge (Leviticus 19:18). The positive side of not bearing a grudge is forgiving “from the heart.” This is what Jesus commands us to do in Matthew 18:35: “Forgive [your] brother from your heart.” The Bible does not say, Make a mere decision to drop the grievance. It says, Experience a change in the heart. The Bible goes even further and commands a certain intensity. For example, 1 Peter 1:22 commands “Love one another earnestly from the heart” (RSV). And Romans 12:10 commands “Love one another with brotherly affection” (RSV).
People are often troubled by the teaching of Christian Hedonism that emotions are part of our duty—that they are commanded. This seems strange partly because emotions are not under our immediate control like acts of willpower seem to be. But Christian Hedonism says, “Consider the Scriptures.” Emotions are commanded throughout the Bible.
The Scriptures command joy, hope, fear, peace, grief, desire, tenderheartedness, brokenness and contrition, gratitude, lowliness, etc.19 Therefore Christian Hedonism is not making too much of emotion when it says that being satisfied in God is our calling and duty.
John Piper, The Dangerous Duty of Delight (Sisters, OR: Multnomah Publishers, 2001), 28–30.