Bitterness is a negative emotion that is not productive in any way, and it can have a devastating effect on your life if you do not let it go. There are many reasons why someone may feel bitterness, and sometimes this emotion is the result of a life of disappointment while in other cases it is due to a single event. When you hold on to bitterness this emotion damages you more than anyone else, and it can cause your life to feel unfulfilled.