In Acts 16 Luke describes a scene where Paul had really wanted to go to Asia to preach the Word, but the Spirit of God had kept him from doing so. Finally, in a dream God tells Paul that its time to go to Asia and preach... there is an open door! Behind the open door there is a woman who responds to gospel, but there are also a few other things waiting for Paul and Silas. They were: stripped, beaten, severely flogged, and thrown in jail. Sort of makes you wonder if you want to walk through the "open doors" that God provides.
Here is the kicker. They are in jail singing (?), and there is an earthquake that shatters the jail walls and they walk out. One of the things that I think we need to remember about open doors is that God calls us to walk through them, to trust him in the midst o the hard parts of life, trusting that he will be faithful. As followers of Christ we are called to see the beauty breaking through the brokenness. We can only see that if we are willing to walk through the open doors that he provides.