I've heard a lot that psychosis can be a spiritual breakthrough/realisation thing, you can be seeing through the construct of reality, either believe you are or actually be, very controversial to claim this of course. If that doesn't resonate with you then you can ignore this part. For me I had a psychotic episode about 9 years ago, it was brought on by the use of legal highs and intense stress at the time. They are strange and I'm sure quite unique for everyone.
It was a feeling of complete loss of control for me, I didn't really know where I was or what was happening. I took an overdose during that time and was sectioned. I said some bizarre things, I was having hallucinations both auditory and visual. It was a terrible experience but when I was back to reality it was like I was born again. How you can tell if you are going into another is a bit hard to say, I guess it would be a feeling of loss of control but as I said they are unique experiences to everyone. If you know what sets them off or are triggers for you this can be good to note.