blessing in disguise 因祸得福，塞翁失马，塞翁失马，焉知非福，塞翁失马，焉知非福

【例句】
This attack proved a blessing in disguise for france.
这次进攻对法国来说最后证明是塞翁失马。

Losing that job turned out to be a blessing in disguise – I found a much better one!
失去了那份工作反倒是因祸得福，因为我找到了一份更好的工作！