Proverbial Mathematics or
Mathematical Proverbs

We have lots of proverbs and quotes which are almost like logical implications. For example,

It is always darkest before the dawn

Mathematically, this translates to:

Dawn => darkest just before

which doesn't necessarily mean

darkest => dawn next

as, one would think, the original proverb is supposed to imply :-)

Another pair of quotes we have are:

All that glitters is not gold (NOT(glitter => gold))
Not all that is gold glitters (NOT(gold => glitter))

meaning gold and glitter are completely "independent" :-)

Can you think of some other similar ones?