人生はギャンブル。Life is a gamble.

Gambling was a common theme of Runyon's works, and he was a notorious gambler himself. 
One of his paraphrases from a well-known line in Ecclesiastes ran: 
"The race is not always to the swift, nor the battle to the strong, but that's how the smart money bets."
競争に勝つのは、速い奴、強い奴とは限らない。
スマートにかけた奴。