In the Bible, the word heart is often a figure of speech for the mind, will, and emotions. God's work of grace is performed in every believer's heart by the Holy Spirit. Through the gospel of Christ, God changes your heart. That is to say, God changes your mind, will, and emotions.
God changes your mind. He transforms your mind by the Holy Spirit (Romans 12:1-2). Then you understand the power of the gospel (Romans 1:16). You repent and receive Jesus as your Lord (1 Corinthians 12:3). Repentance means a change of mind. That change is enabled by the Holy Spirit changing your heart (Romans 2:28-29).
God changes your will. Once you had no desire for Christ. You were unwilling to receive Christ. Now, God has worked in your heart with a desire for Christ (Philippians 2:13). That's the work of God in your heart through the Holy Spirit (Philippians 1:6).
God changes your emotions. Once you had no tender emotions toward Christ nor remorse for your sins. Now, you have godly sorrow for your sins, and emotions of love and gratitude toward Jesus Christ (1 Corinthians 16:22; 2 Corinthians 7:9-10).
