Do any of you have situations where the more you try to focus the more your thoughts conjure up completely and utterly random things?

I'll be trying to think about an apple or the like and then someone comes in an eats it, and I have to "reset" it...

This happens in dreams a lot, and sucks, because conversations usually end up bloodbaths, an then I have to rewind to talking about philosophy. Like if I notice the conversation is going well, a spark in my mind sets off my DC into a monster that I have to rewind. Like if I'm reading an a dark library, something will jar me and I have to reset the entire environment.

This also happens in my thoughts, when you try to think civilly about someone and suddenly imagine them dying or naked. It is extremely frustrating and compromising to your train of thought.

Anyone have this, and anyone know how to get rid of it?