When the Bible speaks of the heart, it is referring to the THINKING INSTRUMENT of the SOUL.
Scripture tell us that the heart is the seat of emotions.  When Paul prays that the “eyes of the Christian heart” be enlightened, he is asking God to help us grasp the revelation of things revealed to the mind. He wants the revelations to move, motivate, and deepen our spiritual insight.  With knowledge, we can then use wisdom to apply the understanding to our lives. 
“I pray that the eyes of your heart may be enlightened in order that you may know the hope to which He has called you, the riches of His glorious inheritance in His holy people.”  Ephesians 1:18 (NIV)
“The eyes of your understanding”: (ophthalmos) + (kardia), “The eyes of your heart.” 
When the eyes of the heart are open and enlightened, we FEEL the power and wonder of the truths written in the Word.  With emotions that are in sync with the spiritual revelations of the mind, a believer can be a highly effective and an honorable vessel or tool of God.  A passionate Christian is highly motivated and ready to serve. They want to understand all things of Christ. Their passion and inexpressible joy is attractive and contagious! Like bees drawn to honey, crowds are drawn to the light within them.
When you face a trial, struggle, or unfathomable circumstance, pray that God opens the eyes of your heart.  The Holy Spirit revelations in your mind will then ignite emotions resting in your heart.  We need to feel the truth in our emotions, yes in the heart-not just in our intellect. 
It is ok to FEEL the truth with our emotions, but it is not ok to be led by the emotions of the heart alone.  Jeremiah 17:9 warns that the heart is impossible to understand and is deceitful.  No wonder the heart needs eyes to see what the mind is learning from God!  
JOY is an emotion our spirit experiences as we chew on the promises and truths of God’s Word.  The eyes of our heart will often rejoice with joy, as our minds comprehend the many promises found in the Bible.  However, we must be careful when other feelings try to convince us to go or do things that are not please God. “It FEELS so good so it must be right” is not always the case.  The heart and mind must find confirmation with the leading of the Holy Spirit and the truths found within the Word.
Everything you do flows from the heart and therefore we are instructed to guard it well. It is the wellspring of our life.  The heart guides and directs us, and every word that comes out of our mouths starts in the heart.  All of our actions and decisions are driven by the desires found in our hearts.  That is why it is so important to ask God to make His desires our desires.
May the wellspring of you life (found in your heart) overflow with joy, as the “eyes of your heart” see and understand how deep His love is for you.  Delight yourself in the Lord, and then He will give you the desires of your heart.  When your will is HIS WILL, how can He deny you? 
“Christ dazzles me and stirs within me such feelings of amazement that I can never get over Him.”  ~AW Tozer 
USE THESE SCRIPTURES FOR YOUR TIME OF REFLECTION 
“Above all else, guard your heart, 
for everything you do flows from it.”      Proverbs 4:23 (NIV)
“The heart is deceitful above all things and beyond cure. Who can understand it?”  Jeremiah 17:9 (NIV)
“Take delight in the Lord,
 and He will give you the desires of your heart.”  Psalm 37:4 (NIV)