Negative emotions usually link to base level survival fears, fear of death. That one is quite strong, and mind finds these emotions much more entertaining than the pleasant ones. It makes the ego feel quite strong, and it doesn't really care that we are miserable as a sideeffect. Negativity easily becomes the way we know we exist. "I complain, therefore I am" sort of attitude, where it actually gives us a sense of personal power to find something to be unhappy about in just about everything.

It sounds like you are so keyed to negative emotions that you have no way to experience positive ones. Many people conclude at this point that the fault lies in LIFE, that life is unfair, life sucks, people suck even worse, and there is nothing to be done but to just hate everything, and everyone, including self, of course. It's great that you are not satisified with this status quo and seek a way out. That is the most critical step, to want to change this situation.

What helped me was to work on the negativity directly. I have found great help in reprogramming my mind in Byron Katie's inquiry method. Once my belief in the stories that evoked negative emotions was cleared there was room to start enjoying the life.