Whom have I in heaven but thee. Ps. 73:25a
The main reason that the godly man has his heart set on heaven is that God is there. It is the dwelling place of his Lord. It is the place where God is gloriously present, where His love is gloriously manifested, where the godly will ultimately be with Him.
He will ultimately get to see God as He really is. He will get to love, serve, praise, and enjoy Him perfectly and forever. If God and Jesus Christ were not in heaven, he would not earnestly long for it.
II. It is the temper of a godly man to prefer God before all other things on the earth.
There is none upon the earth that I desire besides thee. Ps. 73:25b
That which was infused into his heart at his conversion is more precious to him than anything which the world can afford. The views which are sometimes experienced of the beauty and excellency of God are more precious to him than all the treasures of the wicked.
CONCLUSION
(A godly man) is happy because God, who is unchangeable, is his chosen portion. He remains happy because his chosen portion on which he builds as his main foundation for happiness, is above the world, and above all changes.
If a worldly-minded man could find a way to get for himself everything that he could ever want, so that it could never be taken away from him would he be content? No...because all of those earthly enjoyments on which he sets his heart are all fading. But how great is the happiness of those who have chosen the Fountain of all good, who prefer Him before all things in heaven or on earth, and who can never be deprived of Him to all eternity!
Edwards, Jonathan. God, the Best Portion of the Christian. Sinners in the Hands of an Angry God and other Great Sermons by Jonathan Edwards. 137-150.