As in:
spare the rod, spoil
the child.  Don’t spoil
a good time
with meager humor.

Don’t spare the syrup,
just avoid buttering up.
Keep fat in reserve,
like spare change.
Hey buddy,
can you spare me
some time? 

Some leftovers?
Not worth as much
as a strike; leaner,
like a spare tire is
only temporary.
Like a spare room
with little furniture
and bare walls is
only an echo.

Settle on shades 
of gray.  Refrain
from harsh reprimand.
As in:
spare the child, spoil
the rod.