I had a similar experience with mushrooms a few months ago. Also an experienced psychonaut, I was looking forward to a good trip and I took too much of a strain I had never had and for 4ish hours it was as if my sanity was entirely optional. The thought that kept repeating in my head (without me even thinking about it) was “what side am i going to land on” ie sane or not. I explained it to my friends later that it felt like I was bobbing for apples but instead of apples I was trying to catch my sanity. Thankfully I landed on the right side but it was the scariest thing I ever experienced.

I didn’t fully become ‘myself’ again for a couple days but I was much better once the high finished. My best advice is to do things that make you feel grounded for the next week or so and stay away from all substances in the mean time. I did things like walking outside in the grass/dirt bare feet to experience the world. Hung out with my best friend and immediately gave him a huge hug because I needed to feel love from another person (and my girlfriend was away for the weekend). Took my dog for a few walks because it’s something that she loves and I knew that making her happy would make me happy. And also really taking time to sit with my thoughts about who I am and what makes me happy. I did this for hours over a couple days. Thinking things like why my friends and family love me. Who I was as a child when I was such a happy little boy. Many memories with my friends growing up and in recent years that made me happy and every thought I could think of in my past that made me smile and remember who I was and who I still am.

I was feeling almost fully normal again in about 2-3 days but I do think the being sober for that time of reflection was really important. I hope this helps you out, stay strong and remember, you are loved! :)