Tim Keller writes in his book “Prayer”:

In the second half of my adult life, I discovered prayer. I had to. In the fall of 1999, I taught a Bible study course on the Psalms. It became clear to me that I was barely scratching the surface of what the Bible commanded and promised regarding prayer. Then came the dark weeks in New York after 9/11, when our whole city sank into a kind of corporate clinical depression, even as it rallied. For my family the shadow was intensified as my wife, Kathy, struggled with the effects of Crohn's disease. Finally, I was diagnosed with thyroid cancer. At one point during all this, my wife urged me to do something with her we had never been able to muster the self-discipline to do regularly. She asked me to pray with her every night. Every night. She used an illustration that crystallized her feelings very well. As we remember it, she said something like this:

Imagine you were diagnosed with such a lethal condition that the doctor told you that you would die within hours unless you took a particular medicine—a pill every night before going to sleep. Imagine that you were told that you could never miss it or you would die. Would you forget? Would you not get around to it some nights? No—it would be so crucial that you wouldn't forget, you would never miss. Well, if we don't pray together to God, we're not going to make it because of all we are facing. I'm certainly not. We have to pray, we can't let it just slip our minds.