I have read through about seven pages thus far and would like to share my own experiences and opinions.
A few years ago, I had a profound spiritual experience. Everything changed for me and I believed myself to be enlightened. I carried on with this belief for a couple of years, firm in the knowledge that just as I would know if I had fallen into a lake of liquid hot lava and known it instantaneously, I knew I had experienced an all encompassing oneness and the realization of that mystery which is All That Is and God itself. For that moment in time my identity was not and I had all disappeared as 'I'.
In the couple of years that followed I was extremely devoted to my spiritual path as of such. I spent most of my time meditating, conversing with spiritual beings, and being totally immersed in my newfound understanding of life and of myself. But it didn't last. The deeper I went, the deeper I opened myself to the spiritual world, the more out of control I found myself. Finally I had gone so far deep down into the rabbit hole that I completely lost my sanity, became severely dissociated, and believed I was being haunted and possessed by demons.
You cannot imagine the levels of psychosis I went through. At this point I wasn't just having single experiences or visions of the spiritual realm, I was living it 24/7 to the point where I can compare it to drowning with no ability to come up for fresh air. That little sense of 'I' that I had left vanished completely and I lost myself entirely.
I eventually got medical help when my personality fragmented so badly that I regressed to a little child of the age of three years old, unable to handle anymore. My mum had to care for me. It was one of the worst experiences in my life. With the right medicine it took me over a year to recover from that, and to make sense of everything I had experienced and witness.
I finally realized as I got better that all the experiences I had had were at best contradictory and did not harmonize with each other. Including the experience from whence it all started where I believed I had become 'enlightened'. The biggest contradiction was when I was going through the stage where I thought I was possessed, I was 'out of body', in 'heaven' meeting Jesus who appeared to be God. This God was nothing like the experience I had of God during my supposed 'enlightenment'. They were completely at odds with each other. They couldn't have been more different.
In the end I had concluded that I was mentally sick, and that my experience of enlightenment as well as everything else were products of an incredibly complex yet deluded mind. I was hallucinating. Because there is just absolutely no way any of it was real.
Now I do not consider myself to be enlightened or spiritual or anything at all, and I am all the happier for it. My dangerous flirtation with the depths of my own unconscious mind was born out of a deep need and desire to escape from the physical world due to depression and other situations in my life that made things difficult for me. I basically fled into a fantasy world of my own making...
More than anything I accept that the human mind is incredibly incredibly vast, and complicated, and imperfect. I have since become atheistic, but I am glad all that nonsense of my past is behind me.
By the way I am forever damaged because of those experiences. The psychosis left me with incurable chronic fatigue syndrome, non epileptic attack disorder, and other physical issues. In this case I had changed my own neurology so greatly through following these delusions that my body was no longer able to cope, and I doubt it will ever recover.
Therefore whilst I do believe that are benefits to a simple non-theistic spiritual path, I think that religion/spirituality can also be very dangerous and harmful.
Sorry that I have written so much:
TLDR: I experienced enlightenment which made me psychotic and now I'm messed up for life.