Picture yourself walking along a path.  You come upon a boulder in the center of the path.  You can try to move it or just walk around it and continue on your journey.  Next, you encounter a large rock, smaller than a boulder but large enough to clearly see it and avoid walking right into it.

Finally, there is a small rock which can easily be overlooked.  Be careful that you do not stumble and trip over it for that could greatly impede if not completely stop your ability to go forward.  Wounding or severe injury could result that could