I have been writing a weekly blog for almost eleven years now. Over that time, I’ve written several posts on marriage—but never on what might be the most significant issue in marriage.

Let me begin with a humorous story.

Back in 2013, the prominent author and journalist David Brooks delivered the baccalaureate address at the University of the South, which happens to be my alma mater. He began by telling the graduates what not to worry about as they entered the world. Then he said, “Now I’m going to tell you what you should be worrying about.” He continued:

“The first thing to worry about: Will I marry well? This is the most important decision you’re going to make in your life. If you have a great marriage and a crappy career, you will be happy. If you have a great career and a crappy marriage, you will be unhappy. I tell university presidents that since the marriage decision is so central, they should have academic departments on how to marry. They should teach the neuroscience of marriage, the sociology of marriage, the psychology of marriage. Everybody should get a degree in how to marry.”

Brooks then remarks, “Of course, no college president has taken my advice.”

Now to the most significant issue, to which very few people give much consideration when they are entering a marriage.

One of the biggest mistakes we make is believing that our spouse is supposed to be the source of our happiness. This is how many Americans approach marriage: I’m looking to you to make me happy. I’m looking to you to complete my life. But in doing so, we are looking to our spouse to provide something that only God can. Our spouse cannot be God—because we were created with a soul that thirsts for Him.

As wonderful as a spouse may be, as strong and fulfilling as a marriage may become, it cannot satisfy the deepest longing of the human soul.

Consider what David writes in Psalm 42:1:

“As the deer pants for the water brooks, so my soul thirsts for God.”

And in Psalm 63:1:

“My soul thirsts for You in a dry and weary land.”

You may remember when Jesus encounters the Samaritan woman at the well. She clearly was looking for a man to make her happy, to fulfill her life, because it says she’d been married five times and she was currently living with a man. Yet Jesus doesn’t condemn her. Instead, He gently points her to Himself. He recognizes the spiritual emptiness in her life and offers her living water. He says only that living water which He offers will satisfy that thirst in her soul. No man will ever be able to do that.

Richard E Simmons III is the founder and Executive Director of The Center for Executive Leadership and a best-selling author.