That's where a therapist can help guide you or you would have to assess the situation yourself.

If the negative thoughts themselves are what is causing you distress or making you unable to function in some way then the negative thoughts are causing the harm.

Like if you are afraid someone is trying to kill you every time you leave the house, but you know logically no one is, then CBT might be a good technique to help you.

But if someone is actually trying to kill you, law enforcement may be a better able to help you.