The glorious presence of God that the saints shall have of God in heaven is a great part of their happiness
Heaven would not be heaven without the presence of God. The presence of God in the most miserable place possible would be a greater happiness than the absence of God in the most glorious place possible.
David would not be afraid though he walked in the valley of the shadow of death, because God was with him (Ps 23:4). Luther would rather be in hell with God’s presence, than in heaven, God being absent. If the presence of God takes away the dread of the shadow of the valley of death and makes hell to be more desired than heaven, what will the presence of God make heaven to be? The three children in the fiery furnace with God’s presence were happy; how happy then are the saints with God’s presence in heaven?
The saints desire God’s presence even when He is angry; they hate to be out of His presence. In Psalm 51:9 David cried to God to hide His face from his sins, for God’s face was then an angry face against him. Yet in v. 11 he cried out again, “Cast me not away from thy presence.” He was not willing to be out of God’s presence.
Saint Augustine has this expression: “Whose face he fears, even his face he [desires].” God made rich promises to Moses, yet Moses could not be satisfied without the presence of God. “If thy presence be not with us, bring us not hence” (Exod 33:15). The apostle, when describing the misery of those that are damned, in 2 Thess 1:9 says, “Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of His power.”
The presence of God needs to be the happiness of the saints.