Negation

I don’t know why I am quite pessimist about almost everything in life. But don’t get me wrong, I just have negative attitudes only towards me. When I’m with friends or relatives I try to be as positive towards life as I could with them or about things related to them, but it happens to me that I can’t have another vision about my life. If something good happens, I know there will be something bad that will come then. When someone likes me, I know beforehand that it won’t worth. Perhaps it’s fear, but I feel like there always be something bad waiting for me which won`t allow me to enjoy a hundred percent of the good moments. There’s always a "but" for everything I do.
Hundreds of times I`ve tried to think about future and the good things that may come with it, but always the past appears in these thoughts and makes me do some steps backwards, trust me when I say that I do try to let out all the bad things that happened to me but somehow they come back. It is as if I walk one step to the front but then I go back others two. But it’s strange for the reason that these negative thoughts have nothing to do with my career. I try to improve all the time with a lot of effort and being responsible so in the future I can be a good teacher and my students learn something from me. This only has to do with my personal life, which has been quite complicated.