(塞翁失马,焉知非福)
temporary loss may turn out to be a gain.
Life is always full of changes. When facinng loses, we accept it patiently.
When facing gains, we do not overjoy. This idiom is sometimes followed by the second part "yan zhi fei fu　(焉知非福)"，which means "how do you know it is not good fortune"?

learnt it today ! so interesting .LOL