Check out "Wisdom of the Desert" blog HERE, and here is an excerpt:
A brother said to a hermit, "I don't find any disturbance in my heart."
The hermit said, "You are like a door swinging open. Anyone who likes can go inside, and come out again, and don't notice what is happening. If you had a door that was shut you wouldn't let wicked thoughts come in, and then you would see them standing outside the door and fighting against you."