Letters of C. G. Jung: Volume I, 1906-1950 (Vol 1)
To J. Heider
Dear Herr Heider, 1 December 1937
As to your question about X., I can only say the following:
It frequently happens that when a person with whom one was intimate dies, either one is oneself drawn into the death, so to speak, or else this burden has the opposite effect of a task that has to be fulfilled in real life.
One could say figuratively that a bit of life has passed over from the dead to the living and compels him towards its realization.
In the case of X. there was probably an unfulfillment of this kind.
This fact, as said, can either hold you back from life or prevail upon you to live.
It is also probable that, if you are not one with yourself anyway, you get into a conflict, because the bit of life taken over from the dead is of a conflicting nature, both dead and living at once.
As a rule the undifferentiated function always lags behind real life a little and is constantly oriented to the past.
In such cases the unconscious sends out compensatory hints which should be heeded if one has a positive attitude to life.
If something is then undertaken, what passed over from the dead is realized in this undertaking.
As you know, it need not be anything agreeable, it can also be a great difficulty because it always has to do with the still undifferentiated side of oneself and consequently calls up the inferior function.
With kind regards,
C.G. Jung [Letters Volume 1, Page 239]