02/22/2013 02:21 pm ET Updated Apr 24, 2013

Fitness Is Easy, Happy Is Hard

Five years ago, on Valentines Day, I wrote a blog about couples' fitness and strengthening your marital muscles. I had recently designed a six week couples workout program called "Your Marriage on a Walk". Little did I know back then, that my marriage would actually take a hell of a walk, but it wouldn't be with my husband, nor would it be in the same direction he was going.

I read it now and I can't imagine how I wrote it.

The thing about naïveté is that we never feel naive until after. We look back. We cringe.

My advice back then reflected my naive optimism. "Spend the first five minutes when you come home reconnecting with your mate!" and "Take turns reflecting back to each other what you heard your partner say!" Don't forget to "make love" and "have a date night!"

Back then, I think I really did believe that it was this simple: Follow these tips and you will revitalize your relationship.

And fitness is still something I confidently advise others about. I recognize different kinds of limps from across the street and could tell you what part of your back is hurting just by seeing you walk across the room. If you tear your ACL and need some wisdom about healing it, I'm your girl.

But marital advice? I have been humbled. If you ask me about marriage I will shake my head and remain silent. In the same way that we shouldn't take dieting advice from Governor Chris Christie, marital advice is probably best taken from someone more successful at it. In other words, not me.

Still, there are some parallels between fitness and marriage. The slogan "Just Do It" comes to mind. Marital muscles can get stronger and adaptable through consistent and repetitive challenges. It takes work. Or we can interrpret "Just Do It" to mean "say anyway" or "stay for the kids". I am proud that I have been strong enough to not be a wife who did this.

At my gym where I work, I often say that getting to the parking lot is the hardest part. Unfortunately, in marriage, the parking lot equivalent is the altar and anyone who has walked towards one knows that getting to the altar is not hard at all. In fact, it is probably the easiest part of a marriage.

How do we do the emotional, marital version of "Just Do It" when the heart stops wanting to do it? The heart wants what the heart wants. That much I have learned. You wake up one day and your heart knows what your brain doesn't know. Yet. Your body is still here next to your sleeping husband, but your heart didn't even get in bed.

Now sitting here at my desk, I can feel the absence of my marriage, or more specifically the presence of my failed one. But I don't feel only that. I also feel the white silence of motherhood standing behind me, watching and listening. Disappointing my children as well as breaking their hearts is a burden I feel standing behind me, something that won't stand in front of me and can't quite look me in the eye. I have learned to live with this shadow.

And though its been 25 years since I came home at night to an empty house, I am now learning to ride the wave of loneliness as it comes and goes. I have learned to get up quickly when I wake up in the morning. I make my bed while the sheets are still warm so I'm not tempted to get back in.

I divide my day. I go to work at a job I love. I exercise, which always helps. But often when I am teaching a class, I hear my voice talking, but can still feel the sad mom part of me, a shadow at my back.

Still, as we near the end of our conjoined parenting, we are proud that our failure at marriage had nothing to do with anything quite so simple as infidelity or violence or contempt. We earned our way out by trying hard to stay together, by taking our time, by learning to love each other differently and via the legacy of our children.

We have taken a new marriage vow: This is how we will parent our children now. Watch how well we can do this.

Being fit is so hard but it is still so much easier than being happy. Happy is hard. Elusive. Fitness can be obtained through action. You make a list and check things off. Anyone can get fit.

Fitness is obtained via the head but happiness comes via the heart. You cannot think your way to happy. The heart does not have a parking lot.

So here I am five years later, sitting down to write about fitness and ending up once again with a page full of ruminations on love.

The heart wants what it wants.

And I smile reading back through this. Maybe happiness comes when we keep on trying, and hoping, no matter how naive that seems.