"You need to get used to this reality. Once you become a parent, for the rest of your life, you'll never be happier than your unhappiest child, because your heart is tied to your kids. That is a way of learning the gospel because before you have kids you don't really know what it means that God suffers for your sins. He has to. He has to suffer for your sins, because when you have children you suffer for their sins. Your heart is tied up to them."
- Tim Keller, quoted from this Q and A session at The Gospel Coalition