David swore to the Lord, "I will not enter the house I live in, nor lie on the couch where I sleep; I will give my eyes no sleep, my eyelids no rest until I" provide a temple for the Lord to dwell (Ps 132:2-5). David expended much "anxious care" (Ps 132:1) over this ministry. He truly loved and worshipped God, and cared for God's interests more than his own (see 2 Sm 7:2).
The Lord then gave David a prophecy that his kingdom would endure forever (2 Sm 7:16). David was literally staggered by this mind-boggling prophecy of blessing. Read David's prayer of thanksgiving in 2 Samuel 7:18-29. He was overwhelmed, almost "breathless" (see 1 Kgs 10:5), at the unbounded goodness of God.
"God is not unjust; He will not forget your work and the love you have shown Him by your service, past and present, to His holy people" (Heb 6:10). "Eye has not seen, ear has not heard, nor has it so much as dawned on man what God has prepared for those who love Him" (1 Cor 2:18). When you serve God in love, seeking the interests of the Lord and His people rather than your own (see Phil 2:20-21), then God will "open for you the floodgates of heaven, to pour down blessing upon you without measure" (Mal 3:10). "Give, and it shall be given to you. Good measure pressed down, shaken together, running over, will they pour into the fold of your garment. For the measure you measure with will be measured back to you" (Lk 6:38).