First of all: Infinite Regress. All of it. There are thousands of complete personalities being stored inside Seven who she personally assimilated who she doesn't have any conscious communication with under normal circumstances, but they're still there ENSLAVED and tied up to the back of her mind.
(Tuvix times thousands. Janeway is a pussy.)
KIM: Is there anything you don't know?
SEVEN: I was Borg.
KIM: I was Borg. That's what you always say but what does it mean? You've got the knowledge of ten thousand species in your head?
SEVEN: Not exactly. Each drone's experiences are processed by the Collective. Only useful information is retained.
KIM: Still, that probably makes you the most intelligent human being alive.
KIM: So what do you need the rest of us for? Forget I asked. What was that?
SEVEN: Human attitudes toward death are perplexing.
TUVOK: How so?
SEVEN: Too much importance is placed on it. There seem to be countless rituals and cultural beliefs designed to alleviate their fear of a simple biological truth. All organisms eventually perish.
TUVOK: I take it the Borg have no fear of that biological truth.
SEVEN: None. When a drone is damaged beyond repair it is discarded, but it's memories continue to exist in the Collective consciousness. To use a human term, the Borg are immortal.
TUVOK: You are no longer part of the Collective. You are mortal now like the rest of us. Does that disturb you?
SEVEN: My connection to the Borg has been severed, but the Collective still possesses my recollections, my experiences. In a sense, I will always exist.
TUVOK: Fascinating. That must be a great relief.
SEVEN: Yes, it is.
Maybe I wouldn't remember so much if the Star Fleet uniforms were tighter?