Ever since I ran a marathon last December, I’ve been telling my wife that I want to get one of those stick figure tattoos of a marathon runner with the “26.3” caption underneath.

“I think all that running is depriving your brain of its needed oxygen,” she said.

I usually give her the stink-eye when she speaks to me that way, but instead I broke into my best spirit-speak.

“Do you recall that line in the Serenity Prayer that says, ‘God, grant me the serenity to accept the things I cannot change and the courage to change the things I can?’ ”

She rolled her eyes at my elongated enunciation of the word “change.” She knew where I was going with this. She’s bright that way.

“I’ve prayed for the courage to change my lifestyle, and I did. So now I think I should get a tattoo to celebrate.”

“How old are you?” she asked.

I knew where she was trying to take our conversation, but I wasn’t going there. I wanted to go to the tattoo parlor to see a guy named Harley.

The problem was that I was doing what most people do when they spiritualize their language to justify their own desires. I was paraphrasing the third line of the prayer into something like, “God, help me change only what I want to change.”

We can be pretty “courageous” (or in my case maybe foolhardy) when it comes to changing things we don’t like. But the hardest part of the Serenity Prayer is the first part: “Grant me the serenity to accept the things I cannot change.”

We can only pray the first part when we stress the word “accept” in our prayers. In doing so, we commit to a much more difficult course. It’s a course I recommend to many who seek my counsel.

I once counseled a man who was seeking advice on how he might persuade his wife to return home. I told the man to “concentrate on doing nothing.”

“If you have a prayer of seeing her come home, you’re going to have to focus on changing yourself, not her.”

He seemed unimpressed at first, but he’s back with his wife today.

Accepting that we are powerless to change others is rarely easy. In fact, I’m rarely satisfied with that answer myself. In my family life, I’d like to force my son to find a job. In my professional life, I’d like a few of my harshest readers to love me or leave me.

When I committed both these concerns to prayer, guess what? The answer I heard was, “Do nothing. Accept it. There’s nothing you can do.”

The only changes we can really make are the changes we make in ourselves. If those changes are real, and not just simulated, they can have a lasting effect on people.

At the end of the day, I was lying in bed with my wife, still talking about the tattoo, when she asked me one last question.

“You obviously never finished the Serenity Prayer, did you?”

“Huh?”

“Did you pray that last line of the prayer that asks for wisdom to know the difference between acceptance and change?” She pronounced “wisdom” like it was a new concept to me.

She knew my real reward for running the marathon wasn’t what I could engrave on my outsides; the real reward remained in what I felt on my insides.

She’s a smart woman. Still, I wasn’t going to admit that to her. I kissed her goodnight, but I still gave her the stink-eye in the dark.