When I read the books Learned Optimism by Martin Seligman and Negaholics by Cherie Carter-Scott, I recognized myself in many of the descriptions of negative people and negative patterns. I remember a conversation I had with one of my friends in 1994. She called me a pessimist and I said I was a realist. Her response? "All of us experience reality in our own way, but your way is negative."
I didn't agree with her and didn't feel I needed to change at that time... and perhaps I didn't. That world view worked for me at that point in my life. I was young and life was good. But eventually, seeing the world that way did not work for me, so I worked on adopting a more positive outlook. Books like the ones I mentioned above helped me see that thinking negatively was not helpful and was in fact quite harmful both mentally and emotionally. My negative outlook affected me physically as well. I needed to change.
One thing to change was the way I looked at the past. If you have experienced a negative event and you expect the future to be the same, then you naturally tend to be pessimistic. So it helps to revise your memory of the past. Instead of looking at the bad points, think about what you learned or gained from a negative experience.
I understand you may have had a serious trauma in the past. I did too. But there are people who came out of Auschwitz able to love again, able to trust again, able to succeed. Nelson Mandela came out of prison able to forgive and able to lead. These people are not divine masters. They are ordinary human beings. If they can move on from the past, then surely you can too. It takes time and effort but it is possible. When you can look back and see the good points or the learning points of your life, the future seems less scary. You can slowly dial down the negativity until you find that you no longer see the world so negatively anymore. You can have a happy childhood by reframing the way you see the past.
When you feel better about the past, it will be easier to face the future. Now go out and make it a happy new year!