Note from Shelly: From time-to-time, I’m sharing some of the best thoughts from writers/friends that I’ve come across on the web. This guest post is from my friend Amber Johnson, who writes Weddedness, a marriage blog with her husband, Cliff. I regularly follow Amber’s blog because she and her husband have some wise perspectives on marriage after the “I do” part…and well, they’re just funny writers to boot. Read this, and then visit her blog as well.

Ten  years ago, when Cliff and I got married, he had hair and I had thighs that would have fit into skinny jeans, had they been stylish then. I was shy in groups and reticent to ever express a strong opinion; Cliff was more brash. He was headed for a career in social work. I wanted to be a writer.

Cliff was thinking about converting to Catholicism. I thought women shouldn’t be pastors. We weren’t positive we wanted kids. Everything we cared about could fit in the trunk of our car.

Now, Cliff has moved past Catholicism: our pastor’s name is Laura. I’ve learned to share my opinion, and occasionally cross the line to brash; Cliff has softened his voice. He’s left social work behind and is now in non-profit management. I’m on the same career path. We own a house full of stuff, though the things we care about mostly still fit in the back of our car: safely buckled in two car seats. And the hair and thighs, well, time changes things.

Here’s what I’m trying to say: who I married on September 8, 2001, isn’t quite the same person in my bed tonight. The change has been gradual, but the differences are stark. In fact, our son recently looked at a picture from our wedding day, and asked, “Where are you guys?” Good question.

We’ve been lucky: we’ve changed roughly in step with each other. Many of the changes have been for the better (I’ve learned to be more direct; Cliff has learned to listen more). And we’ve developed the thick skin it takes to tolerate the changes that are a bit tougher to stomach.

Not everyone is so lucky: some changes take more adapting. Think of the career woman who decides to be a stay-at-home mom. Or the stay-at-home mom who finds herself yearning for a career. Either occupation is respectable, but a sudden and passionate swing from one to the other can unsettle a relationship, especially for a husband who thought he was married to one and finds himself working out weekly schedules and budgets with the other.

I know of other families where one partner has suddenly become a serious runner, requiring hours of Saturday morning training runs and changed diets for the whole family.

And what if your husband becomes more brash? Your wife more bossy? What if illness or parenthood or unemployment changes something fundamental about your partner’s personality? Even if only temporary, the result can be feeling like you’re in bed with a stranger.

Ethicist Lewis Smedes says of his marriage, after 25 years, “My wife has lived with at least five different men since we were wed – and each of them has been me.”

What do we do about this? The answer isn’t to avoid change. The answer is to somehow respect the changes in each other, change in step when you can, and give your spouse space to be who he or she needs to be when you can’t. I think the answer also lies, somehow, in the promises we make to each other.

Smedes writes that “when I make a promise to anyone, I rise above all the conditioning that limits me.” Essentially, you have to rise above who you are and who you see yourself with to be open to who your partner is becoming. Let the promises you made be the through-thread of your relationship, when other things seem less certain. Find unlimited potential in who you could become together. Find excitement in being in bed with someone new.

Tim Keller, in his book The Meaning of Marriage, quotes Smedes (above) and then offers this wisdom: ”Over the years you will go through seasons in which you have to learn to love a person who you didn’t marry, who is something of a stranger. You will have to make changes you don’t want to make, and so will your spouse. The journey may eventually take you into a strong, tender, joyful marriage. But it is not because you married the perfectly compatible person. That person doesn’t exist.”

Amber Johnson works at the Center for Values-Driven Leadership in Chicago, IL. She and her husband, Cliff, are the proud parents of Sam and Maggie.