"For it is with your heart that you believe and are justified..."
Romans 10:10

Scripture has much to say concerning the heart, let's see what the Word opens up to us today. One thing we know is that the heart has to be made ready to receive the good news of salvation. It is God alone who does so, while man tries to meet his own needs.
"For by grace you have been saved through faith, and that not of yourselves; it is a gift of God." Ephesians 2:8

If we consider the heart as the center of life-- The heart needs to be carefully guarded:
"Keep your heart with all diligence,
For out of it springs the issues of life." Proverbs 4:23

The heart determines character:
"For as he thinks in his heart, so is he..." Proverbs 23:7

The heart also is the source of evil:
Jesus explaining a parable to the disciples (Read Matthew 15:15-20):
"Do you not yet understand that whatever enters the mouth goes into the stomach and is eliminated? But those things which proceed out of the mouth come from the heart, and they defile a man." Vs. 17-18 It would be good to read Vs. 1-20 for the full understanding.

The heart controls speech:
Jesus speaking in Matthew 6:45,
"A good man out of the good treasure of his heart brings forth good; and an evil man out of the evil treasure of his heart brings out evil. For out of the abundance of the heart his mouth speaks."

The heart is the source of faith:
"For with the heart a person believes (adheres to, trusts in, and relies on
Christ) and so is justified (declared righteous, acceptable to God), and with the mouth he confesses (declares openly and speaks out freely his
faith) and confirms [his] salvation." Romans 10:10 in the Amplified Bible

As Believers then--
Love God with all your heart:
A Pharisaic lawyer's question and Jesus' response, "Teacher, which is the great commandment in the Law?
Jesus said to him, 'You shall love the LORD your God with all your heart, with all your soul, and with all your mind.'" Matthew 22:36-37

Sanctify God in your heart:
"But in your hearts set apart Christ as Lord. Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect." 1 Peter 3:15 (This is one close to my heart, my hope is that we all can give an answer for the hope that it in us.)

Trust in the Lord:
"Trust in the Lord with all your heart,
And lean not on your own understanding;
In all your ways acknowledge Him,
And He shall direct your paths." Proverbs 3:5-6

Do not regard iniquity:
"If I regard iniquity in my heart,
The Lord will not hear." Psalm 66:18

Do God's will:
"Servants, be obedient to those who are your masters according to the flesh, with fear and trembling, in sincerity of heart, as to Christ; not with eye service, as men-pleasers, but as servants of Christ, doing the will of God from the heart." Ephesians 6:5-6

Thank you Lord God for Your light in our hearts:
"For it is the God who commanded light to shine out of darkness who has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ." 2 Corinthians 4:6 Yes, the very same God who said, "Let there be light and there was light." Genesis 1:3

Holy Spirit lead and guide us in all our ways that we may, in heart, mind and will, be unto Almighty God all that is pleasing to Him. Amen