Keep thy heart with all diligence; for out of it are the issues of life. Proverbs 4:23 KJV
The heart is the fountain from which the river of words flow bringing death or life.
Death and life are in the power of the tongue: and they that love it shall eat the fruit thereof. Proverbs 18:21 KJV
Our hearts actually think. The heart has, according to science, 40,000 neurons and it moderates the thoight process of the brain. In our heart is our conscience. There is the communication center of our spirit.
What we truly believe comes out of our mouth in times of crisis (stress, pressure, etc.). If you want to know your faith level, listen to yourself during those times.
O generation of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh. Matthew 12:34 KJV
Guard your heart. Deposit the Word of God in your heart, not just in your head. There, let the Spirit and the Word agree and listen to the sweet, life gving, river of words flow from your lips.