The Law of Undulation: Remaining Steady in Christ When Your Teenager is Anything But 

A quick Amazon search reveals that there are over 10,000 self-help books available to parents of teenagers. Titles include: How to Talk So Teens Will Listen and Listen So Teens Will Talk (this writer must have girls), Have a New Teenager By Friday: From Mouthy and Moody to Respectable and Responsible in Five Days (good luck with THAT), and Yes Your Teen Is Crazy! Loving Your Kid Without Losing Your Mind (too late). 

Trying to relate well to a teenager feels something like trying to walk across a waterbed. Their moods and whims swell and roll beneath our feet, constantly keeping us off balance and wondering what invisible current may knock us to our knees next. As I navigated my own teenagers’ unpredictable moods, I found a steady footing in C.S. Lewis’ explanation of the “law of undulation.”

In his classic volume on spiritual warfare, The Screwtape Letters, C.S. Lewis imagines what a shrewd demonic strategy might look like in the life of a Christian. Uncle Screwtape, a senior devil, writes to his nephew Wormwood, a junior devil who has been put in charge of a newly converted Christian man. Wormwood’s goal, of course, is to undermine the unnamed Christian’s faith by any means necessary. His “affectionate” Uncle advises him in a series of witty and insightful letters.  

In the course of the instruction, Screwtape spends a couple of letters outlining what he means by “undulation.”

According to Screwtape, “undulation” means that human life is a series of “troughs and peaks.” Humans, he explains to Wormwood, are “amphibians- half spirit and half animal.” This means we exist as both spirits in eternity and bodies in time. The spirit of the Christian can stay steady (which we know is made possible by the power of the Holy Spirit), but his mind, body, will and emotions are subject to change. Like waves on the ocean (or a waterbed), these highs and lows are inevitable- hence, the law of undulation.

Screwtape shows Wormwood how this works “in every department of his (subject’s) life- his interest in his work, his affection for his friends, his physical appetites, all go up and down. As long as he lives on earth periods of emotional and bodily richness and liveliness will alternate with periods of numbness and poverty.” 

I know exactly what Screwtape is talking about. Some highs are higher and some lows are lower, but there is undulation in the course of my day, my week, my year, and certainly across seasons of my life. But my teenager has no experience with these natural fluctuations. So the low of failing the driver’s test or being left off the invite list feels like the end of the world. The high of winning the 400 meter hurdles produces a cocky and unreasonable expectation of winning every race. 

Teenagers Experience Highs and Lows Differently Than Adults

Younger children aren’t quite so aware of these highs and lows, but teens experience undulation as a roller coaster, alternately terrifying and exhilarating. Teenagers tend not to understand that neither the highs nor lows last very long. Our kids veer unpredictably from the depths to the heights and back again, and they seem determined to take your whole family with them for the ride. 

Keeping this law of undulation in mind helps me empathize with my teen, and therefore be a little more patient with the moodiness and drama. It can be hard for a parent to remember what a first crush felt like: he loves me!!! He loves me not… But to the extent that I can remain calm for my child in those swings, I help her regulate strong feelings such that their intensity does not overwhelm. Experience tells me that this won’t be her only unrequited crush, so I can remain connected and kind and unworried, even in a torrent of her tears. I also know that Jesus can meet her in the rejection she feels, and I pray with her with confidence in his ability to comfort her.

Remain Steady in the Lord, With and For Our Teenager

Of greatest interest to Wormwood is how this law applies to his Christian subject’s faith in God. If the demon can catch his man in a “period of numbness and poverty” with God, he might succeed in damaging the fellow’s faith. 

I know the ups and downs of mood, energy, emotion, and well-being in every aspect of my life, especially in my walk with God. I can remember the seasons when God seemed very near and real, and the seasons when I wondered if I had made him up in my head. 

Spiritual maturity means recognizing that while some of the lows have been very long and very low, God has never left me to fend for myself, and he never will. This maturity brings freedom from pursuing spiritual highs because we learn to rely on his goodness without needing mountaintop experiences. 

The key to stability, or, as the Bible calls it, rest, is to trust that no matter how high the highs or how low the lows, God holds me steady, firm, constant and true. Furthermore, he is making me as steadfast as himself. Recognizing the fluctuations in my own life, and relying on God’s steadfastness through them all, can help me avoid a rollercoaster of fear when my child experiences seasons of doubt and seasons of zeal. 

But teenagers who are learning to walk with God might not be as cognizant of these fluctuations as their parents are.. When reading the Bible becomes boring, worship feels uninspired, and prayer seems fruitless, our children need reassurance that God has not abandoned them. When our child returns home after “the best mission trip ever” he will need his parents to be sympathetic yet steadfast when he comes crashing down from spiritual highs. 

Screwtape begrudgingly admits that this is what God teaches parents and teenagers alike in our “dry seasons,” those low points in our faith and circumstances when we cannot feel or see the Lord at work. The “troughs” are about learning to live by faith, not by sight (2 Cor. 5:7). 

A Sure and Steadfast Anchor of the Soul

As Screwtape teaches us, some of what our families experience in teenage undulation may stem from spiritual warfare, the attacks of the enemy against God’s beloved people. Spiritual forces of evil would like nothing better than to keep parents and kids doubting God’s goodness, too unstable to plant their feet on the Rock who is Christ. 

Hormones, immaturity, and inexperience make our teenagers vulnerable to wild swings of emotion and inconsistent behavior. As parents who love them, we need faith and perseverance to avoid overreacting to their highs and lows. If we swing with our child into the depths of anger or sadness or frustration, we won’t be able to give them the perspective they need.

Which is why we need Jesus, the “sure and steadfast anchor of the soul” (Heb. 6:19). We—and our kids— have a God “abounding in steadfast love and faithfulness” (Ex. 34:6), who has demonstrated his steady commitment to us throughout history. Before the foundation of the world, he determined a plan for our salvation. He encouraged us with promises of salvation and reconciliation with himself, and then fulfilled those promises on the Cross of Christ. His track record of steadfast love towards us is so perfect that we eagerly anticipate the coming Kingdom because we are sure it is coming. We know our God will not waver nor fail, and that knowing steadies us. 

No matter which way the waves roll today, this is a God we can trust with our kids. 

For more gospel-centered parenting resources, check out our current Rooted Parent Podcast season: Parenting, Technology, and the Truth. 

Anna is a single mom of three young adult sons. She is the Senior Director of Content at Rooted, co-host of the Rooted Parent podcast, a member of Church of the Cross in Birmingham, AL, and the author of God's Grace for Every Family: Biblical Encouragement for Single Parent Families and the Churches That Seek to Love Them Well (Zondervan, 2024). She also wrote Fresh Faith: Topical Devotions and Scripture-Based Prayers for College Students. In her free time, Anna enjoys gardening, great books, running, hiking, hammocks, and ice cream. She wants to live by a mountain stream in Idaho someday.

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