As believers, we are in a daily battle - not against others but against our thoughts (Ephesians 6:12). The negative thoughts we get bombarded with each day have the potential to affect our actions. Jesus showed us how to win by knowing the Word in His mind and His heart (Matthew 4:1-11).
It's not enough to know the Word in our mind by memorizing verses. We must know it in our heart. When reading the Word and God leads you to a verse or verses, circle them. Read over previous chapters to get the full context. Then pray on them. It takes time, but the Word will impact your heart and you'll become more than a conqueror in Jesus (Romans 8:37).