I Am My Own Worst Enemy!

I have seen this appear a couple of times in my horoscope and I would have to agree with it. I can conjure up all sorts of things in my mind - both good and bad - but for the most part they are mainly bad. I think of the most worst situations and in reality they hardly ever come to pass. Why can't I just think positively? I do try to do that but its like there is this constant battle between the good thoughts and the bad thoughts - with the bad thoughts usually winning. I definitely have to work on this more!