Actually, Rosie, believe it or not, you can stop your mind from doing this.... And please understand that I am in no way meaning to sound patronising or superior, truly.
It's just that I know, through comments, input and posts that you have contributed, that you have experienced a far worse time in your life, than most, on here....
I don't normally do this, but I would urge you to seek out a centre near you that practises meditation... Zen is usually good, and Tibetan is also very helpful. Maybe also somewhere that teaches Yoga, or tai Chi...
I hesitate to recommend you read any books specific to Buddhism, because as a Buddhist, I am discouraged from preaching, "spreading the word" or proselytising.
But I would like to help you, and convince you that truly, the chief and only Mistress of your mind is, and can only ever be, you. If you'd really liketo convert the negatives into positives, it can be done. And you can do it.
With metta and Karuna,
Alexandra