Answer
Negative feedback always tries to restore body conditions back to the set point. Positive feedback is a self-amplifying cycle in order to lead to a greater change. Because positive feedback promotes and produces change, it doesn't try to restore body conditions back to the set point, often disturbing homeostasis.
Work Step by Step
The whole point of positive feedback is to promote a rapid change, not restore conditions back to normal, which is the goal of homeostasis. In addition, the self-amplifying cycle of positive feedback doesn't allow conditions to loiter around a set point, instead it pushes conditions to one extreme.
