Emotions are states of mind. Count pessimism as one of your negative emotions! You are a wise person because you know that you have negative emotions. You are wiser person because you are looking for the solution. The best approach to change the negative emotions is Dhamma. You have to practice Dhamma dynamically. Dhamma is a scientific practice which eradicates negativities from the mind and fill the mind with positivity. I have been practicing myself; I am a live example.