For me, there are three ideas that I got from Jung that I find most helpful (and not at all harmful). First, that a symbol can mean infinite things (so a mother-symbol could be both comforting and threatening -simultaneously- or paradoxically). Second, we are engaged in a sort of ongoing "conversation" or even power-struggle with the unconscious, like being on a see-saw with a somewhat uncooperative, occasionally hostile partner. Third, life is a quest for something "sacred" and if you read Arthurian literature, it overlaps with alchemy (i.e., the search for the sacred "essence" which connects us to Eternity).
However, there is one idea that is (I wouldn't say "harmful" but) a bit misleading, taking you on a roundabout path where, if you stop to rest, you end up in error. And that is the idea of the Self. Of course Jung had no misconception but the word might be unfortunate. It seems each person has to experience first-hand that the "Self" is really strangely, beautiful but exceedingly strange.
Just as an anecdote, one day (I'm in my 50's) I looked outside my window, and saw what seemed to be the planet Saturn, and it was so striking and beautiful, big and round with the rings. It was huge, taking up much of the sky, and of course not "really there" (my wife couldn't see it). Each of the rings was a road or highway, busy with trucks and cars driving along, carrying on whatever business, seemingly so close and so far from where I stood in my little house. It was just over the trees.
Somehow I knew I was witnessing this "Self" that I had cluelessly sought for so long, but it was so bizarre and oddly impersonal. It seemed "out there" and had no regard for "personal me," the overweight guy in the mirror, the one paying the mortgage, the one struggling with morality, the one consumed and confounded by all the little snares of a very average middle-class life. It was so utterly detached from "me" and yet I felt it was compassionate somehow, "merciful" because it showed itself to lowly, imperfect me. Words fail to capture even a miniscule slice of this strange joy. My life was changed forever. But outwardly, exactly the same and even today, my heart still leaps just to recall.
Long story short, there is no "personal self" but there is -something- that we see which is simultaneously "out there" and "in here" which has a luminous, numinous, mystical quality. And that is the Goddess, the Grail, Eternity, redemption, Heaven, "wholeness," or as Jung called it, the Self.
So the quest to discover the Self leads us to something so very opposite to what we expect. Jung laid it out so clearly but how can anyone understand this until it happens? A thousand books and 30 years of grasping brought me no closer. It came on an ordinary day, on its own, no asking.