First, lets talk a little human psychology. In basic terms, peoples emotions have two levels: the presenting behavior is the part above the surface you can see and hear; beneath, the underlying feeling is what motivates the behavior. Imagine a grandfather whos grumbly at a family holiday dinner: the presenting behavior is that hes cranky, but the underlying emotion is a sad sense of loneliness from his family never seeing him. What good negotiators do when labeling is address those underlying emotions. Labeling negatives diffuses them (or defuses them, in extreme cases); labeling positives reinforces them.

Never Split the Difference by Chris Voss