As capable as you are, there is always someone more capable, just as there is another heaven beyond heaven.

解释 ( paraphrase )
天空之外还有更大的天空，人之外还有更强的人。
这条谚语告诉我们：做人一定要谦虚谨慎，切不可狂妄自大，因为在你的周围总会有本领和能力超过你的人。

This proverb advises us to be modest and prudent no matter how talented we are, because there is always someone better than we are at something.

同义词 ( synonym )
强中自有强中手，能人背后有能人。

造句 ( example )
每个人在新的环境中都要有紧迫感，不能放松自我，自以为是，要知道天外有天，人外有人的道理。