Emotions must have played an important role in our evolutionary past. Emotions guide our most primal behaviors. I hypothesize that animals whose cerebral cortex are less developed, live a more emotional life.
I believe our emotions were very useful in the more primitive environments in which we evolved: the hunter gatherer society.
Emotions range from fear which prepares an organism for fight or flight.
Many people let their emotions govern their behavior. I think to thrive in today's society it is better to be in control of your emotions as much as possible. To be cool as a cucumber, calculating, precise. Our emotions were designed for simpler times. Its our job to use our intellect to shape our emotions to help us get ahead.
In my case, I would like to show loving compassion to my family and close friends as much as possible. Everybody else is one among many, anonymous. Treat these people in a way that benefits you the most. Be polite with everybody but do not tolerate their bullshit. Remember that people are a commodity in great surplus. If they give you trouble there are literally millions of people out there who can replace them...