In those towns that the Lord your God is giving you as a special possession, destroy every living thing. You must completely destroy the Hittites, Amorites, Canaanites, Perizzites, Hivites, and Jebusites, just as the Lord Your God has commanded you. This will prevent the people of the land from teaching you to imitate their detestable customs in the worship of their gods, which would cause you to sin deeply against the Lord your God. Deuteronomy 20:16-18 NLT
The command to destroy every living thing sound rather harsh, until you understand why.
The Lord said to Moses, "You are about to die and join your ancestors. After you are gone, these people will begin to worship foreign gods, the gods of the land where they are going. Deuteronomy 31:16
God knows the human heart, human nature. He knows that we start to imitate that which we are around. It's the "garbage in, garbage out" principle. God knows how easily our hearts can be swayed and that's why He gave this command. The Israelites were commanded to destroy every living thing, but in Deut. 13:13 and Deut. 15:63, we read that they didn't fully obey this command. As you continue to read their history, you see that the Israelites did indeed turn away from God and begin to worship other gods.
God had plan and a purpose.
He has a plan and purpose for your life too. Is God calling you to get rid of some things from your life? Is He asking you step away from certain relationships? Has He asked you to remove certain television shows from your viewing? Maybe God has asked you to get rid of some music or books. Remember that He loves you and wants to guard your heart. He knows what is best for you. Listen to His call and fully obey. God has a plan and a purpose!