In The Spirit of Disciplines, Dallas Willard writes about seeing Holman Hunt's famous painting called "The Light of the World" at St. Paul's Cathedral in London. The painting depicts Revelation 3:20: "Behold, I stand at the door and knock; if any man hear my voice, and open the door, I will come in to him, and I will sup with him, and he with me." The painting's interpretation at St. Paul's reads "On the left-hand side of the picture is seen this door of the human soul. It is fast barred, its bars and nails are rusty; it is knitted and bound to its stanchions by creeping tendrils of ivy, showing that it has never been opened."
But the door, according to the passage in Revelation, on which Christ is knocking is not the door of the human heart as is suggested. Rather, it's the door of the church at Laodicea. Willard explains, "We will get nowhere in our attempts to understand the gospel, the church, and our own lives today unless we understand that Christ is outside the church as we commonly identify it." Every church claims to have Christ inside it. While we wish that were true, he is definitely on the outside. For Christ is really in the world (the only place great enough for him), where those in the church lack the courage to follow him fully.
So, why is Christ trying to come in? His words to the church in Laodicea just a few verses earlier are not particularly complimentary. They are said to be neither hot nor cold. Because they are lukewarm, Christ says he will spew them out of his mouth. Even so, Christ is still knocking. Maybe it's because he knows that the people in the church, though lacking, should still be the best prepared to freely receive him and cooperate with him and are the best hope to help fulfill his vast purpose for humanity and the world. Of course that preparation won't just happen without an intentional commitment of those inside the church to take Christianity seriously.
Taking Christianity seriously requires discipline. Willard identifies 7 disciplines when we abstain from our normal desires (food, sleep, bodily activities, companionship, curiosity, sex). These he calls these Disciplines of Abstinence: solitude, silence, fasting, frugality, chastity, secrecy and sacrifice. He then identifies 7 Disciplines of Engagement: study, worship, celebration, service, prayer, fellowship, confession and submission. We don't have to commit to all of these disciplines, but we should want to do most.
Meanwhile, he's still knocking. He hasn't given up and won't.