Ecclesiastics and Song of Songs

The writer set his heart to seek and explore... everything.... wisdom, folly, madness, pleasure, wealth, work, love.

Here the words used for heart  are - mind, self, strivings, thoughts.

As he sets about exploring the world's pleasures, he finds that it is all futile, vain, empty.  In fact, it is downright despairing.  You work hard and do well, but when you die you leave it all to a foolish son who just wastes it.  No matter how hard you work, there is never true rest.

But,  God, " made everything appropriate in its time. He has also set eternity in (our) heart, yet so that man will not find out the work which God has done from the beginning until the end."
The writer realizes that God judges both the righteous and the wicked.
That God tests us so we can see our own beastly hearts.
That we need to stop and think about death, to be serious about life, because of eternity.
The hearts of men are full of evil and insanity.. but in wisdom we can direct out minds and hearts to God.   All is in His hands.  He is the giver of gladness and true joy.

In the Song of Solomon the use of the word heart is used in reference to the love of the groom and the bride.
His heart is glad on his wedding day.
His heart beats faster when he sees his bride.
Her heart awakens at his voice.
He tells her that he will be a seal over her heart - a love that is stronger than death, protects her heart.

Jesus, the bridegroom, looks forward to the day when He will gather His bride!  What a wonderful thought!  His heart beats faster for us. Our hearts awaken at His voice. He has set His seal, His Spirit over our hearts!  Precious thoughts.

Father,  thank You for reminding me once again, that nothing else is of value except You.  You have set eternity in my heart. Without knowing You, there is nothing of value in this world.  But, knowing You, we can know joy and gladness in all things!  Keep our hearts set on You.  Keep my heart Lord, directed towards the right, in wisdom and truth.  Amen