A bird in hand is a certainty. But a bird in the bush may sing.

A bird in hand is better than two in the bush

Don't the wounded bird still sing?

One big vice in a man is apt to keep out of a great many smaller ones

And I hear from the outgoing ship in the bay The song of the sailors in glee: So I think of the luminous footprints that bore The comfort o'er dark Galilee, And wait for the signal to go to the shore, To the ship that is waiting for me.

The only sure thing about luck is that it will change.