I don't think it's possible for any person to understand another perfectly without knowing each other a long time. We're all coming from different places.

That said, IMO, ultimately the point of therapy is not for another person to understand you. It's nice to be understood and it can help, but really the point of therapy is for you to understand you. So maybe if you return to therapy ever, you could try thinking about the therapist as someone who might not understand but can help you understand. Sort of like how a physical therapist can help an injured person walk again, regardless of whether they've ever been injured themself.