You have made a typo:
either they never knew what they really want to do = they were confused and didn't know what to do [they didn't really know what to do]
they've spent so much time in doing what they have to do = they have planned much time on doing something
invested so much "psychic capital" that they are completely lost without it = they have gained so much desirable mental states that they are completely lost without them. [if they ignore the "psychic capital" (desirable mental states), they will fail.]
lost without it (them) = lost without the desirable mental states. [failed without it (them)]
I wish you could give us a source and say to us that where you found the text and what the text was about.
Without much context or source, it's a little difficult to analyze it.
(I'm not a teacher)
Interested in Language