One Brick at a Time

Walls are built one brick at a time. Initially the bricks along the ground are a mere nuisance. We trip occasionally, stub our toe and curse vainly. Imperceptably the wall grows and poses more of an obstacle and hinderance. Until finally, one day, all we can see is the wall. We are suddenly alone and strangely surprised by this situation. Where did this wall come from? When did it grow so high? How did this happen to me?
If only we had noticed each time we laid a brick down. One brick is easier to remove than an entire wall.