Ideally they won't be negative after working on them using CBT. In CBT, you have to be aware of your thoughts too, but instead of thinking "is this thought useful to me", you think "is this thought an accurate representation of my current situation". You then work on changing your thoughts until it is an accurate representation of your current situation. Categories like "mindreading" and "catastrophizing" mean that you are assessing a situation with incomplete information, and training your brain to not make snap judgments can be immensely more helpful than training your brain to just ignore those snap judgments. It does take a lot of work, but a lot of the time the thoughts you need CBT or mindfulness to work through, you get because there's an unresolved conflict in your life that you can't find a resolution for. It's better to train your brain to find a resolution for problems than to ignore them.