Driving down a country road, a man came to a very narrow bridge. In front of the bridge, a sign was posted: "YIELD." Seeing no oncoming cars, he continued across the bridge and to his destination. On the way back, he came to the same one-lane bridge, now from the other direction. To his surprise, he saw another YIELD sign posted. Curious, he thought, "I'm sure there was one posted on the other side." When he reached the other side of the bridge and looked back, sure enough, yield signs had been placed at both ends of the bridge. Drivers from both directions were requested to give right of way. It was a reasonable and gracious way of preventing a head-on collision.
When the Bible commands Christians to "be subject to one another" (Ephesians 5:21) it is simply a reasonable and gracious command to let the other have the right of way and avoid interpersonal head-on collisions.