My "Shadow"

I'm looking for someone who is familiar with Carl Jung's theory of the subconscious and stuff, specifically the "shadow" of the subconscious.

If you are not familiar with the shadow and want to tell me that this is something evil or dark or unhealthy or something, please refrain from doing so, I have heard quite enough from people I've asked for help who weren't even willing to listen to me explain what it is.

I had met my shadow and it stuck around for a while, I actually thought it was a tulpa for a while (google it if you're not familiar with what a tulpa is, it's very interesting) Anyway, he, or it, (not sure whether it is a male or if it just chose to take on that gender when presenting itself) was actually really cool, he was only around for like 3-4 months and I absolutely loved having him, I loved talking with him, and he seemed like a reasonable voice to consult in if I was confused or something, because he wasn't really biased about most things and saw things without any emotions getting in the way.

My problem is he disappeared a long time ago and I want him back, and I think i know what happened. I really think I've "assimilated" him (which is the term on the wiki page about it) or rather, I've sortof...absorbed him? So that he's in every part of my mind, and he isn't separate from everything anymore.
He's no longer himself, but part of me, and it feels wrong, I feel completely wrong and it's been almost 5 years now. I haven't heard his voice or felt his presence in my mind since then. Basically, when he "disappeared," I suddenly felt like my mind had become a small room, compared to the giant endless void it felt like when he was there. It was like a wall just appeared and I could no longer access all that space in my mind, if that makes sense. I also have a hard time making decisions, and an even harder time staying focused on things than before. (I have ADHD, so focus is already awful)

He was sort of a companion to me, so my question is, can you "un-absorb" your shadow? And how am I supposed to do it exactly? I need to separate him from my conscious, because I don't really think he's in my subconscious anymore, which is where he's technically supposed to be. A friend had suggested trying to find something I don't accept about myself, or...I guess "unaccepting" something I had previously accepted about myself? I apologize if this is confusing to everyone, I hope someone can understand what I'm talking about.

Un-absorb will be impossible. For he is you, and will always will be. However, what you may have really done, is block off this part of yourself from your mind. You may have never absorbed this part of yourself after all. Maybe that is why your mind felt like a small room. You closed your mind off from him.

Is there a way I can re open it? Thank you

Just accept yourself, your feelings, and your thinking. Do not try to look for things to make yourself feel bad about yourself.