If you're a fan of the television show House, then you know he says that patients always lie. And you know, he is right, uncomfortable though that may be to accept. Eery one of us has experiences, feelings, thoughts that we keep secret from everyone else. And everyone includes the therapist. Therapists know this and know that part of the work we do is to endeavor to make the therapeutic space safe enough for our patients to begin to reveal secrets and in the process discover that doing so does not bring all the terrible things they have feared.
Jung knew and addressed this very issue:
The inferior and even the worthless belongs to me as my shadow and give me substance and mass. How can I be substantial without casting a shadow? I must have a dark side too if I am to be whole; and by becoming conscious of my shadow I remember once more that I am a human being like any other. At any rate, if this rediscovery of my own wholeness remains private, it will only restore the earlier condition from which the neurosis, i.e., the split-off complex, sprang. Privacy prolongs my isolation and the damage is only partially mended. But through confession I throw myself into the arms of humanity again, freed at last from the burden of moral exile. The goal ... is not merely the intellectual recognition of the facts with the head, but their confirmation by the heart and the actual release of suppressed emotion. (Jung, CW 16, p134)
It isn't enough to simply be able to say it, though that is a big piece, but also to feel what has been held private, and in that the secret loses its hold on us and we become freer.
So you'd think it would just be a matter of knowing this to make it so. That therapists could tell patients this at the outset and it would all be so much easier. But secrets are well-defended and yield reluctantly to being exposed. So it takes time. Sometimes a very long time. But the effort is worth it.
I think in many ways the goals of therapy are fully accomplished when the patient no longer feels the need to keep secrets from the therapist, when she feels the freedom to say all of it, no matter what it is, when he can truly say whatever comes to mind. Ad maybe none of us ever fully gets there but it is more than possible to go a long way toward that goal.