Value, of course, is a two way street. There must be a subject for whom a certain object is valuable. Moreover, this relation must be constituted by distance. We express this with the truism "You don't know what you have until it is gone." Perhaps a more cynical way of expressing this, however, is "You don't know what you're chasing until you have it." That is to say, the high value we put on the unattained objects of our desire quickly lose that value when we own the object and thus experience it as "ours".
An example of this is the (modern?) relations between a man and a woman. Some people are said to love the chase, the cat-and-mouse games, that exist as two people encounter each other as potential partners. The other is at a distance, not quite within our grasp, and so the games exist to draw the other closer, perhaps out of genuine desire for the other, or perhaps out of a desire to be genuinely desired by the other and thus boost one's ego or temporarily distract oneself from loneliness. But once the distance is closed, once the object (or subject) of desire becomes ours, something is lost. We are, in this sense, unable to enjoy. This is the irony of what some consider to be the "hedonistic age" in which we live. Simmel explains value in this way:
...value does not originate from the unbroken unity of the moment of enjoyment, but from the separation between the subject and the content of enjoyment as an object that stands opposed to the subject as something desired and only to be attained by conquest of distance, obstacles and difficulties.
I don't know if Simmel's choice of the word "conquest" intends this, but with this word he exposes our relations to the world as being one of violence. Violence is commonly thought of as a getting rid of the other. But in the Western world, perhaps its more common form is just the opposite: rather than getting rid of the other, we desire to bring the other close to ourselves, within our grasp, but always as its owner or master. In short, we desire to possess. That which we possess has little value. That which we do not possess has the potential to be enormously valuable, until we possess it.