It is too late to lock the stable door when the horse is stolen.
More French Proverbs:
You are either hammer or anvil.French
Never trust a woman who mentions her virtue.
French
He sleeps securely who has nothing to lose.
French
Shear the sheep but don't flay them.
French
Why hide from God what the saints already know?
French
One tale is good till another is told.
French