If some of the emotion-generating systems are the same in animals and humans, then studies on animals can help understand some of the human behavior. The brain mechanisms that generate conscious feelings are not different from the mechanisms that generate cognition. Emotions happen to us. We hardly will them to occur. Perhaps that's part of their advantage.
Emotions are powerful motivators of human behavior.
Like other vestiges of evolution, however, they sometimes help us succeed or be happy and sometimes they cause us trouble.