The meaning of ‘partially and often only self-deceptively reduced’

the meaning of ‘partially and often only self-deceptively reduced’

The passage below comes from 'Dreams, Illusion, and Other Realities'.

https://books.google.co.kr/books?id=WgtCCQAAQBAJ&pg=PA77&dq=%22partially+and+often+only+self-deceptively%22&hl=en&sa=X&ved=0CBwQ6AEwAGoVChMIt_Hs_7CpxwIVCSmUCh05tAUO#v=onepage&q=%22partially%20and%20often%20only%20self-deceptively%22&f=false

We can, it is true, tell our dreams to someone else and, if we are lucky, his imaginative response to them may give us the illusion of a shared experience. But if the person we tell a dream to turns out to be a sceptic, we have no means of convincing him that we really did have the dream we have told him. If he asks for proof that we had that precise dream and no other one, that we have remembered it correctly, we cannot give it. We cannot ask the people who appeared in the dream to confirm our story. Unlike the events of everyday life, which can, in principle, be confirmed or otherwise by the laws of evidence,... dream experiences have a peculiar privacy about them, which can only be [partially and often only self-deceptively reduced] by recounting them to others.

In this passage, as I understand, dream experiences can only be [partially and often only self-deceptively reduced] by recounting them to others because dream experiences have a peculiar privacy about them.

(Am I right?)

Now, what I really want to ask is what the underlined 'partially and often only self-deceptively reduced' means.

How does telling someone your dream make them [=dream experiences] reduced?

(I can't accept the idea of REDUCED DREAM.)

And how they are 'partially and often only self-deceptively' reduced?

(Even though I accept the idea of REDUCED DREAM, I cannot figure out how it is reduced 'PARTIALLY and often only SELF-DECEPTIVELY'.)

Regards.