The need for connection.

One of the most basic needs of man is the need to connect to Hashem.  If we don't connect to Hashem we take this basic need and connect to something else.  This can be the source of real problems, because we will never fill this need by turning to anything other then Hashem.

from a Shiur on Naaleh:
Elul: The Sweetness of Tikkun Hamidot

Teacher: Rebbetzin Tziporah Heller Class: Elul and Rosh Hashana: Days of Closeness and Awe

In OA there is a saying- "Trying to fill a God sized hole with a man sized thing"  We can indulge in all of the pleasures of this world and we will never feel satisfied.