STEP OR STUMBLE

I just read the following poem that reminds me for every action there is an equal and opposite reaction. By analogy for every action directed toward us we react to it in some way.
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"Stepping Stone or Stumbling Block"

Isn't it strange that princes and kings
and clowns that caper in sawdust rings
And common folk like you and me
Are builders for eternity.

To each is given a book of rules
A block of stone and a bag of tools
For each must shape ere time has flown
A stumbling block or a stepping stone.