It's a cliché that many Christian converts are initially zealous, but either become lukewarm or drift away from the faith. Why is that? What, if anything, can be done about it?
I'm sure that this is much more prevalent among men than women. Let's take a stereotypical case. A man converts to Christianity. He learns the basics of Christian theology. He may identify with a particular theological tradition. He learns the jargon. He proselytizes all his friends, relatives, and coworkers. He has debates over creation/evolution, Calvinism/Arminianism, cessationism/continuationism, millennialism/premillennialism, Catholicism/evangelicalism, credobaptism/paedobaptism, &c. He's drawn to controversial and intellectually challenging books like Romans and Revelation.
But after a while, there's a sense in which he's just running in place. What does he do for an encore? Is this all there is to the Christian life? That's when the post-conversion letdown sets in.
Some converts maintain momentum by becoming pastors, evangelists, missionaries, apologists, or seminary professors. However, even in that case, there's the danger of reading and writing, speaking or debating, as an intellectual diversion. A way to pass the time. A distraction to alleviate tedium.
Men tend to be more interested in theological ideas than women. This is true of men generally. More male philosophers, theologians, bloggers, &c. Men like to debate ideas.
New ideas are apt to be more exciting than familiar ideas. So what happens when you feel that you've learned the ropes? Where do you go from there?
One problem is that a lot of Christian laymen have a very superficial knowledge of Christian theology. They could dig a lot deeper. There's also some good Christian fiction.
However, another problem is if we view the Christian life primarily in terms of head knowledge. Now, many Christians would benefit from expanding their head knowledge. They are woefully ignorant.
Ultimately, though, the Christian faith isn't a quest to discover new theological ideas, but to internalize theology. Let it sink in. Become marinated in Christian theology. Live out your faith. Become what you believe. Fidelity. Sanctification. Putting your faith into practice.
To take a comparison, I believe it was Leland Ryken, in Windows to the World, who said great literature is inexhaustible. If you come back to the same book years later, you notice things you missed before. You have a newfound appreciation for an old story.
The story hasn't changed–you have! Life changes us. Although the story is the same, the reader is not the same. Every time you return to the story, you see it through the lens of your own, layered experience. Even though you know the plot, there's something new to you each time you read it because different things resonate with you based on your evolving life experience.
That isn't just true of literature. It can be true of movies and TV dramas.
And that, in turn, has an analogy with the walk of faith. Some Christians stall. For some Christians, the road runs out before the destination because "they've heard it all" before. Now, as a matter of fact, most of them have a very shallow grasp of Scripture and Christian theology. They have lots more to learn. Even if they applied themselves, in the course of a lifetime they'd still be scratching the surface.
Even so, there are limitations to that orientation. The walk of faith is not primarily an intellectual adventure. It's not about discovering what lies over the next hill. If that's your approach, that's an invitation to boredom.
Rather, the walk of faith is more about using "old" ideas, familiar theological truths, to understand the events in your life. To interpret your experience. Births and deaths. Marriage. Child-rearing. Friendship. Betrayal. Illness. Aging. Hope. Frustration. Disappointment.
Use theology as the filter to make sense of these events. Try to find meaning in these events.
Finally, this life is supposed to be disappointing. Supposed to be unsatisfying.