from "Relationships: A Mess Worth Making" by Tim Lane & Paul Tripp":
"God keeps us in messy relationships for His redemptive purpose....
Have you ever wondered why God doesn't just make your relationships better overnight? We often think that if God really cared for us, he would make our relationships easier.
In reality, a difficult relationship is a mark of His love and care. We would prefer that God would just change the relationship, but he won't be content until the relationship changes us, too. This is how God created relationships to function."