The effect of emotional venting is to sustain an unsatisfactory status quo. Most people think the opposite, that complaining is part of an effort to change an unsatisfying situation. Nope. Complaining lets off pressure so that we neither explode with frustration nor feel compelled to take the often risky steps of openly opposing a difficult person or situation. Keeping emotional pressure tolerably low doesn't change problematic circumstances but rather perpetuates them.
Reference: Martha Beck