Emotions affect more in an individuals life, than one may think they do. They affect how we act, how we respond to situations and how we think. Emotions are biological and instinctual, no one sits you down and teaches you how to be sad, happy, or angry, they are natural responses to a situation. They have been around forever and have been beneficial to the survival of man kind. Emotions and feelings are quite powerful and have the ability to influence someones life for the better, or for the worse.
Depending on how an individual is feeling can impact their entire thought process. If a person is depressed, lonely, or experiencing any other negative emotion, they are going to think darker and more bleak, the glass half empty. While someone who experiences emotions of happiness and has a more cheery disposition is more optimistic and is more likely to achieve positive goals.
Every person handles different situations in their own unique way, and their is no "right" way or "guide" that tells you how to react. For instance losing a loved one, one individual may be moved or motivated into a deep depression, while another may just feel the urge to cry. On a more positive note, getting engaged, someone may scream and become animated and scream while another may cry, tears of joy hopefully. All responses are different and acceptable but are motivated by the same situation.
Fear, anger, joy and sadness all push us to either laugh, cry, scream, run away, or surprise us and do the exact opposite of what our normal character may do. Either way you look at it emotions are strong, influential forces inside every one of us.