The image of the bridge is a beautiful metaphor. On the bridge you have two points, two ends. Normally we think a person should have only one standpoint, but when you become a bridge you have to have two. This is also a kind of explanation for the concept of crossing the border of the self: as one person, you should have many standpoints. Between these two points, there is one that is more stable, your original personality and another point which is less stable, floating. This bridge is always dangerous.