Emotions are close to the core of our being.
Often, when negative feelings are expressed, a listener will say "don't feel sad" or "you shouldn't feel that way." The one whom expressed their feelings then feels embarrassed and believes that it's not okay to verbalize true feelings. Communication then regresses to a safer level, that being a level where deeper feelings are hidden.
Emotions should be accepted and reinforced. We often label emotions as bad whereas it's the role that they play in life that we should consider.
Emotions express our true selves and how we are feeling. To allow another to express emotion, without criticism or scorn, allows connection to another at a deeper level. It allows vulnerability and to know another better.