A stepping-stone can be a stumbling block if we can't see it until after we have tripped over it.

A stepping-stone can be a stumbling block if we can't see it until after we have tripped over it.

如果我们在被踏脚石绊倒后才看到它，那么它就是绊脚石。

-- Cullen Hightower 卡伦高塔