Cool as a cucumber.
More Traditional Proverbs:
While it pays to be honest you are often a long time collectingTraditional
Seed money.
Traditional
If you think you're leading and no one is following you, then you're only taking a walk.
Traditional
Who is wise He who can learn from every man
Traditional
Dismantle the bridge shortly after crossing it.
Traditional
Fortune helps him that's willing to help himself.
Traditional