Answer:
Turns us on our backs, and open up our stomachs. You will be the wisest of men though at start a lummox.
What surrounds the world, yet dwells within a thimble?
Though blind as well, can lead the blind well.
It is a part of us, and then replaced. It escapes out bodies, to a better place. The world becomes its sizeable home. Its passions unrestraint, the planet it roams.
Gets rid of bad ones, short and tall. Tightens when used, one size fits all.
What is always coming but never arrives?