Not that you have the time to do this, but if you went around and interviewed EVERYONE who has done therapy for 3+ years, they would overwhelmingly (90% +) tell you that they reached a place where it felt useless, hopeless, pointless & ineffective.
Some of them quit, some of them continued.
Those that continued discovered that things ACTUALLY WERE changing in small ways, but that they were unable to (or inhibited from) notice the improvement. All they could see was the very familiar (if uncomfortable) OLD VERSION of themselves.
There is a deep & powerful evolutionary program in your psyche called “homeostasis preservation”. It means that your whole identity and worldview has become inexorably linked with your sense of stability and familiarity in the world. Everything you’ve learned since 7 yo is built upon these core assumptions & beliefs.
When good therapy starts to change you, this program gets activated by a lot of unconscious fear, and that program starts to bias the evidence you notice. It deletes & distorts what (the evidence) you pay attention to. And this gets you back into that hopeless & depressed place (familiar). It also gives you a very good (illusory) reason to give up and quit your efforts at change.
In addition the the interviews I’ve described above (to prove what I’m telling you), all you can do is be transparent with your feelings, plus be patient and ride-out this terrible state of fear & destabilization.
Here is an example of someone else in a similar place
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Dewey Gaedcke’s answer to Is it likely that some people are genetically predisposed to codependency?
Dewey Gaedcke’s answer to What are the benefits of seeking therapy?