“I say to the Lord, “You are my Lord; I have no good apart from you.”” (Psalm 16:2, ESV)
David not only declares his exclusive trust in and loyalty to the Lord, but he acknowledges Him as the ultimate and unique source of all good.
Aristotle noted that there are some goods that are good for the sake of other goods, such as money, for example, and medicine. These are not goods in and of themselves. You can spend money to buy things that make your life better and you can take medicine that makes you feel better when you are sick, but accumulating a pile of money or a cabinet full of medicine are not all by themselves beneficial in any way. They are goods for the sake of getting things or getting better. When we get the things we (properly) desire, or get better, we are ultimately seeking happiness (The Greek word is eudaemonia, also translated human flourishing). In short, he argues that it is for the ultimate good—happiness—that all other goods are sought.
For the virtuous Pagans, this is a reasonable conclusion. For the Christian, however, who has received the ultimate revelation in the person of Jesus Christ as recorded in the Scriptures, we know the ultimate good is a Person. As the Westminster Shorter Catechism reminds us, the chief end of man is to glorify God and enjoy him forever. There is no good apart from Christ.