There is an old story told about the dilemma of a monkey reaching down through the narrow neck of a glass jar to grab the alluring beads contained within and to which he is irresistably attracted. 

In excitement and desire, the monkey grasps a full handful of beads to pull out and possess. But the constriction of the jar's glass neck means that his clenched fist can only be withdrawn with just one bead held. Any more, alas, and the hand is too full to pass!

If we are the monkey, Advent is the glass jar and the prize we try to grasp is Jesus at Christmas.