Everything acts according to its nature. Maple trees put down roots, grow pointed leaves that turn red in autumn, and drop their leaves every year because that is what they were made to do. Kittens play, eat numerous times a day, and purr in your lap because that is their nature. People also act according to their nature. Without Christ, they do as they please because sin thwarts their ability to live a righteous life. However, those of us in Christ have regenerated hearts and have the ability, by the power of the Spirit of God, to act according to our new natures, obeying God with gratitude and joy.

Have you ever watched a small child play with a shape sorter? She tries to put a cube into a round hole and gets frustrated. Then she tries to put the star in the square hole, and that doesn’t work either. But when she finds the sphere that fits the hole, she crows with joy because she matched the right shape with the right hole.

So it is with us. Our joy comes in matching our nature with our actions. When we act against our new nature in Christ, we only find sorrow and disappointment. We are no longer content with the things of this world because they don’t fulfill our needs. We are made for eternal things now.

In the letter to the Colossians, Paul tells us to put off the old man and instead follow our new nature in Christ:

But now you yourselves are to put off all these: anger, wrath, malice, blasphemy, filthy language out of your mouth. Do not lie to one another, since you have put off the old man with his deeds, and have put on the new man who is renewed in knowledge according to the image of Him who created him, (Colossians 3:8-10).

Is Paul just being a killjoy here? No, he is stating the truth–we have new natures and our only joy will be in following who we are in Christ. Our old nature enjoyed the fleeting pleasures of this world and wanted its own way, but those things don’t fit our new nature. It’s like taking a shower and putting on the dirty clothes we shed before getting clean. Donald Grey Barnhouse wrote,

We are told to put on the Lord Jesus Christ, and to make no provision for the flesh, to fulfill the lusts thereof (Rom. 13:14). In other words, our old Adamic nature is compared to a dirty garment which we are to lay aside as we would lay aside any soiled clothing, and we are to put on the new man as we would put on clean, fresh linen.

Barnhouse, D. G. (1963). God’s Heirs: Romans 8:1–39 (p. 18). Grand Rapids, MI: William B. Eerdmans Publishing Company.

Do you want to feel joy in your life? Find it in obeying Christ. I once heard a pastor say that we often have at least one thing that we should be doing and aren’t or that we shouldn’t be doing and are. Think of that thing, and do it or stop doing it. At first, it may be hard and maybe you won’t feel happy about it. Eventually, however, joy will bubble up in your heart as a result of the Holy Spirit working, and in Him, you will find fullness of joy.