You stop believing it. Just because you believe something, doesn’t mean it’s real.
If talk therapy isn’t doing anything for you, then do something else.
It’s incredibly difficult but the best way, perhaps the only way…
Medication as well
Talk therapy, unless it’s a goal oriented one like CBT or DBT, is mainly just for venting. A good therapist will also help you realize patterns you fall into and help you understand yourself better, but all the work really must be done by you, so it is not the best therapy for everyone.