A recent study by Cornell University concludes:
... people get more enduring happiness from their experiences than their possessions ...
Possessions have value only to the degree that we consider them "ours" but nothing belongs to us forever. Possessions will deteriorate, loosing their novelty and value over time. Still, we work so hard to acquire, retain and protect them. Those efforts are ultimately futile, hence the inherent dissatisfaction with possessions.
I'd like to emphasize the experience of letting go as exemplified by the chorus of The Streets'
Everything Is Borrowed:
I came to this world with nothing
And I leave with nothing but love
Everything else is just borrowed