Deuteronomy 11 gives two reasons why the Israelites were to take heed to themselves,
“Take heed to yourselves, lest your heart be deceived, and you turn aside and serve other gods and worship them, lest the LORD’s anger be aroused against you, and He shut up the heavens so that there be no rain, and the land yield no produce, and you perish quickly from the good land which the LORD is giving you” (Deuteronomy 11:16-17).
First, taking heed to themselves prevented them from going after idols, or other error. Second, taking heed to themselves prevented them from experiencing the wrath of God.
Friends, we need to take heed to ourselves for the same reasons.