It it really self inflicked? Or are these thoughts because you are not really into her?
If you think you are really into her, and you think about the problems relationships can have - then you have a habit of thinking this way. Think about how into her you are more often than the habitual worries. Amplify the feelings of how great the realtionship is.
I wouldn't know why you cultivated a habit like this, but maybe there was a reason it helped you to think like this but now you can start to see that it doesn't help you now. Maybe you once were with someone you weren't too into and you started this way of thinking during that past relationship. And now you dig this girl and your conditioned self is trying the same thing as an emotional protection mechanism.