Objection 1. It would seem that enjoyment is only of the end possessed. For Augustine says (De Trin. x, 1) that "to enjoy is to use joyfully, with the joy, not of hope, but of possession." But so long as a thing is not had, there is joy, not of possession, but of hope. Therefore enjoyment is only of the end possessed.
Objection 2. Further, as stated above (Article 3), enjoyment is not properly otherwise than of the last end: because this alone gives rest to the appetite. But the appetite has no rest save in the possession of the end. Therefore enjoyment, properly speaking, is only of the end possessed.
Objection 3. Further, to enjoy is to lay hold of the fruit. But one does not lay hold of the fruit until one is in possession of the end. Therefore enjoyment is only of the end possessed.
On the contrary, "to enjoy is to adhere lovingly to something for its own sake," as Augustine says (De Doctr. Christ. i, 4). But this is possible, even in regard to a thing which is not in our possession. Therefore it is possible to enjoy the end even though it be not possessed.
I answer that, To enjoy implies a certain relation of the will to the last end, according as the will has something by way of last end. Now an end is possessed in two ways; perfectly and imperfectly. Perfectly, when it is possessed not only in intention but also in reality; imperfectly, when it is possessed in intention only. Perfect enjoyment, therefore, is of the end already possessed: but imperfect enjoyment is also of the end possessed not really, but only in intention.
Reply to Objection 1. Augustine speaks there of perfect enjoyment.
Reply to Objection 2. The will is hindered in two ways from being at rest. First on the part of the object; by reason of its not being the last end, but ordained to something else: secondly on the part of the one who desires the end, by reason of his not being yet in possession of it. Now it is the object that specifies an act: but on the agent depends the manner of acting, so that the act be perfect or imperfect, as compared with the actual circumstances of the agent. Therefore enjoyment of anything but the last end is not enjoyment properly speaking, as falling short of the nature of enjoyment. But enjoyment of the last end, not yet possessed, is enjoyment properly speaking, but imperfect, on account of the imperfect way in which it is possessed.
Reply to Objection 3. One is said to lay hold of or to have an end, not only in reality, but also in intention, as stated above.
Source: Summa Theologica (New Advent)