פילוסופיה בגרוש

It always amazed me how one can have a perfectly healthy body and feel comfortable with himself.
But then, it is enough that he'll get the smallest paper-cut, which is in less than 0.0001% of his body tissues
and immediately his all consciousness is focused on that insignificant part of his body.

What is it about pain, that consumes our all and change our entire perception in a heartbeat?