Have you ever thought what is the most important thing that we should guard?
"The time is coming," declares the LORD, "when I will make a new covenant with the house of Israel and with the house of Judah. It will not be like the covenant I made with their forefathers when I took them by the hand to lead them out of Egypt, because they broke my covenant, though I was a husband to them, " declares the LORD. "This is the covenant I will make with the house of Israel after that time," declares the LORD. "I will put my law in their minds and write it on their hearts. I will be their God, and they will be my people.
God spoke about the New Covenant, and the word is very clear that it'll be written in the hearts. Infact, the Bible tells us that the heart is the source of life.
"Keep your heart with all diligence,
For out of it spring the issues of life." -Proverbs 4:23
In the Bible, God made us all aware that the Satan is Cunning (Shrewd).