Fulfilment is a function of time

If you evade suffering you also evade the chance of joy. Pleasure you may get, or pleasures, but you will not be fulfilled. You will not know what it is to come home.
[...]
Fulfilment, Shevek thought, is a function of time. The search for pleasure is circular, repetitive, atemporal. The variety-seeking of the spectator, the thrill-hunter, the sexually promiscuous, always ends in the same place. It has an end. It comes to the end and has to start over. It is not a journey and return, but a closed cycle, a locked room, a cell.
Outside the locked room is the landscape of time, in which the spirit may, with luck and courage, construct the fragile, makeshift, improbable roads and cities of fidelity: a landscape inhabitable by human beings.
It is not until an act occurs within the landscape of the past and the future that it is a human act. Loyalty, which asserts the continuity of past and future, binding time into a whole, is the root of human strength; there is no good to be done without it.

Ursula Le Guin, The Dispossessed (Gollancz, 2002) pp. 275-276