This is a story I heard at a seminar once, from a very trustworthy source.
A missionary was down in Haiti, (or a similiar Satan worship/ black magic filled area). He had been preaching and meeting with great opposition. The forces of evil were strong in that area.
He awoke one night, laying alone in his tent. He lay still on his cot, facing the tent wall.... But something was wrong. He wasn't alone. He could feel the presence, an evil presence in the tent with him. There was a sense of darkness, death, oppression all around. The air seemed thick with dread, foreboding death.
As he wakened, and realized this was no dream, he rolled over in his cot, not knowing what to expect. Sure enough, he wasn't alone. In the doorway of the tent, inside, was evil itself. It appeared to be Satan standing there, sucking . all the light and life out of the room. The tent was filled with evil. Satan had found him, and was opposing him with all the forces of hell.
But, this man was a child of the most high, walking in God's promise and purity. His heart was safe. In the midst of evil itself, the missionary simply said "oh, it's just you" and rolled back over to sleep.
Satan has no power over us, when we walk in God's way. There is no reason to fear. None is greater than our God.