The Biblical heart refers to our way of thinking and our thought life. It includes our will and the resulting emotions. Do you think about the goodness of God and his blessings, or about the bad things and curses? What you think about you bring about, as it comes out of your mouth!
Carefully guard your thoughts because they are the source of true life. Ask Holy Spirit to open up the Word of God to you, as you read. Meditate on Scripture and it will give you a healthy thought life. Since life flows from your mind, it is important to protect it because your thoughts run your life. Positive or negative talk will come out of your mouth, depending upon your thoughts and give birth to life or death.
Guard your heart above all else, for it determines the course of your life. (Proverbs 4:23 NLT)
Your words are so powerful that they will kill or give life, and the talkative person will reap the consequences. (Proverbs 18:21 TPT)