To desire is to want something beyond you, and in approaching it your psychology dredges forth all the pains of wanting and not receiving, all the failures of the past. 

Even if we receive what we crave it disgorges the toxins simultaneously, causing us to flinch away as we grasp, causing sabotage as we approach fulfillment. 

This desire/repulsion creates a loop of approach and retreat: a self-frustrating and painful cycle.