When negative people feel down, certain tactics--like being told to cheer up or calm down--never work. Instead, they usually want you to understand where they're coming from and where their lives are at right now. Maybe they're overwhelmed with commitments they can't let go of; maybe they're between jobs, going through relationship problems, or are trying to gain stability in their lives. Regardless, they just want someone to share in their feelings with them and to feel like they're understood. Often, that alone will be enough to cheer them up.