In What Way Man Should Be Enjoyed
36 For if we find our happiness complete in one another, we stop short upon the road, and place our hope of happiness in man or angel. Now the proud man and the proud angel arrogate this to themselves, and are glad to have the hope of others fixed upon them. But, on the contrary, the holy man and the holy angel, even when we are weary and anxious to stay with them and rest in them, set themselves to recruit our energies with the provision which they have received of God for us or for themselves; and then urge us thus refreshed to go on our way towards Him, in the enjoyment of whom we find our common happiness. For even the apostle exclaims, “Was Paul crucified for you? Or were ye baptized in the name of Paul?” and again: “Neither is he that plants anything, neither he that waters; but God that gives the increase.” And the angel admonishes the man who is about to worship him, that he should rather worship Him who is his Master, and under whom he himself is a fellow-servant.
37. But when you have joy of a man in God, it is God rather than man that you enjoy. For you enjoy Him by whom you are made happy, and you rejoice to have come to Him in whose presence you place your hope of joy. And accordingly, Paul says to Philemon, “Yea, brother, let me have joy of you in the Lord.” For if he had not added “in the Lord,” but had only said, “Let me have joy of you,” he would have implied that he fixed his hope of happiness upon him, although even in the immediate context to “enjoy” is used in the sense of to “use with delight.” For when the thing that we love is near us, it is a matter of course that it should bring delight with it. And if you pass beyond this delight, and make it a means to that which you are permanently to rest in, you are using it, and it is an abuse of language to say that you enjoy it. But if you cling to it, and rest in it, finding your happiness complete in it, then you may be truly and properly said to enjoy it. And this we must never do except in the case of the Blessed Trinity, who is the Supreme and Unchangeable Good.
Source: Christian Doctrine (New Advent)