Greek to me?

In my Greek translations, I recently ran across a number of proverbs. Apparently the textbook likes these proverbs—especially the ones expressing futility. I thought you might enjoy some of them (they are mostly my translation):
 

You are spitting into the sky.

You are devising a small rope out of sand.

You are singing a victory song before the victory.

You are bringing the war engines after the war.

You are shaving the lion.

A big book is a big evil.

A bad egg is of a bad crow.

The roughness of a road tests the usefulness of a donkey.

The wolf changes his hair, not his purpose.

A mob is a poor judge of beautiful things.

Lions at home, foxes in battle.

You are writing on water.

You are seeking milk from a bird.

You are lending light to the sun.

One proverb sounds suspiciously like a mixture of Shakespeare and Julius Caesar: “The world is a stage; life, an entrance—you came, you saw, you went away.” Just remember, though, “without health, life is lifeless.”