Have mercy on me, O Lord, for I call to you all day long. And is it possible for a person to pray all day long? Only in this world, which is a day for the nations of the world and a night for Israel. But I call to you all day long. Rejoice the soul of your servant, for to you, O Lord, I lift up my soul. Bar Kappara says, if a person has a servant and says to him, "I will buy you a garment," he is happy. How much more so if a person says to his flesh and blood servant, "Serve me," are we happy to serve you, O Lord. Rejoice the soul of your servant.
Soul of Bar Kappara
Midrash Tehillim 86:2