Introducing a child into your life will, similarly, lead to some increase in tension for most people. Less charitably, people will tell you that children will “ruin your marriage.” It is easy to see why this might be. You and your partner both want the best thing for your child—indeed, you want this more than anything you’ve ever wanted. However, most of the time you have no idea what this “best thing” is. And you’ll sometimes disagree, either due to deep underlying differences or simply because you both have no idea and your best guesses differ.