Presumption

After all this that Josiah had prepared for the temple, Neco king of Egypt marched up to fight at Carchemish by the Euphrates, and Josiah went out to confront him. - 2 Chronicles 35:20

It seems that after King Josiah repaired the temple (and led in the process of returning the nation back to God), he went on to make some assumptions. Perhaps because he had been so faithful, Josiah thought that any decision he made on his own would be blessed by the Almighty. He was riding a winning streak, so apparently he thought why not just go for it. The king of Egypt was outside of his borders, possibly seeking to expand his empire, so Josiah boldly went after him without first consulting Yahweh, the God of Israel. The results were disastrous.

Josiah's error is often made. We assume that God is on our side in a decision because we have been faithful, yet clearly God is faithful (above all else) to His glory and His name. "Riding the wave" of spiritual victory can often lead us to make assumptions that result in defeat. Wisdom demands that we check our bearings (and attitudes) often. While past faithfulness is important, present faithfulness is paramount. Every thought must be captive to Christ. Every action must be weighed in the balance of His truth as we seek to avoid the sin of presumption.

God does not suffer presumption in anyone but Himself. - Herodotus