What does 2 Kings 14:9 mean?

But Jehoash, king of Israel, replied, 'A thistle in Lebanon sent a message to a cedar tree: Give your daughter to my son as a wife. But a wild animal passed by and trampled the thistle. You have beaten Edom and now you're arrogant. Enjoy your victory, but stay home. Why stir up trouble that will only bring you down and Judah with you?' 2 Kings 14:9 - Modern Text Bible

(Jehoash warns Amaziah not to let his pride get him into a fight he can't win, using a parable to make his point.)