Probably the difference has everything to do with behavior.

When I was young, I would see people in my room, outside my window, etc, very frequently, at night. Sometimes I was terrified and would go awaken my father to get rid of the person...but the person was always gone by the time my father would arrive. Based on my father's behavior, I received the understanding about imagination and dreaming and sleepwalking, etc. To me these people were completely real, and completely present. Even now, when I remember some of them, they still seem completely real. But since nobody else ever saw them, I learned, in these situations, to accept that this was something that just happened to me and it was not to involve other people. In other words, I still had the experiences, but I behaved outwardly in a socially approved way. Eventually I just ignored the people, and by the time I was a teenager I rarely had night visitors. 

Had I not been able or willing to absorb/intuit that understanding, and if I behaved and talked as if there were real people visiting me, I might have been viewed clinically as a disturbed, psychotic child. So in my case, there were no changes in experience...just changes in behavior. 

Last year, I was talking to someone who is long diagnosed with bi polar disorder; it's a large part of their identity. It seems to cause a lot of problems in their life, due to their behavior, and I was asking them what kind of symptoms they experience. As in, how do they KNOW when a bi polar circumstance is arising. One of the symptoms is that the radio talks to them personally. I asked "But do you KNOW that you are believing something that you don't believe at other times, and that other people don't believe?" The answer was yes. Well, I didn't understand how the bi polar circumstance could occur, as in, the strange behavior, which was really what caused all the problems, because in my experience, if there was an awareness of what bi polar is, and awareness that bi polar is happening, then behavior could be modified (consciously not acting out like this person does). But at that point, we were clearly unable to understand and relate to one another! 

So I think one can have private experiences that could be considered clinically delusional or psychotic, but as long as one still behaves in a socially-acceptable way (or doesn't complain about the problem), then it is not a psychosis. Pointing to psychosis being more about culture and classification, and not so much the individual experience.

Another thought, I have two friends who have talked about their acid flashbacks. One will see a bat fly over them, swooping by their head. This happens to them most often while riding the city bus. It's always startling and they always react visibly to the bat that only they can see, shooing it away, protecting their head.  This sometimes is disturbing to other passengers. The other friend's flashback is while they are driving their car, they suddenly are in a carnival ride type of situation, like those swan boat cars that go through water tunnels? This in no way affects their driving, they simply 'drive' the carnival swan car through the water tunnel!

If you were watching each of these people, one would look like their conscious reality was altered (psychotic), and the other, nothing would even be visible (normal).

In your real life example, the first time you feel like you have died and are in a realm with angels, etc, you don't have any way of knowing what the social protocol is for that environment! So you behave in ways that are possibly labeled psychotic. However, if you ever have that experience again, you might now approach it with more insight and awareness, because of the prior experience, like "what makes me think I'm dead" or "what makes this woman seem like an angel"? Then it becomes a mystical experience rather than a psychotic episode, in my opinion. Awareness is everything!

And when you explore an outward mystical experience in an internal way, you thus become a Mystic. :)

I have had similar experiences to this, when I was a teenager. I had been experimenting with street drugs, and for months afterwards, started to hear voices that seemed like they were coming from in the room with me, having confused / delusional thoughts and acting strangely. It was very frightening at times, and seemed to be very real.

I think that the difference between someone with "psychic" abilities and someone with psychosis due to mental illness or drug abuse can be a bit blurred. Mystics have often used various drugs to enhance their abilities, throughout history, and they can supposedly help to alter perception, enough to see things that are really there, but can't be seen by most people. I am a skeptic myself, and my hunch would be that they are just high, but then again, I had a pretty weird experience once, when I was hanging out with some friends, and some of them started saying that they could see spirits moving around in the room, and took out a digital camera and started taking pictures, and we could all see them in the pictures. One of them was actually so solid, that you couldn't see the TV behind him. So maybe there really are things that are there, but just aren't visible to most people.

Meditation can also supposedly enhance psychic abilities, and cause people who have no abilities at all to start to hear and see things that aren't visible to the average person. So it may be that all people are "psychic" to some extent, or at least have the potential to be. There are lots of different things that can be considered "psychic" abilities, like clairvoyance and telepathy especially, but also include telekinesis, intuition, levitation, energy healing (laying on hands, Reiki etc.), and aura reading, to name a few. The only one that I know of which has been proven to exist is the ability to produce unusual amounts of heat from the palms of one's hands, in the case of healers (and it's debatable whether this is actually more effective at treating discomfort or any sort of illness than a hot water bottle, or a placebo). I can actually do this myself, to some extent, and my mother used to be a Reiki master, which makes me wonder if some of the unusual experiences that I've had could have been more than just a hallucination. I still do occasionally hear "voices" (not like they were before, though, just very faint buzzing or ringing when I concentrate, and once in a while it seems to have the cadence of speech), but nothing like it was before, when I was having the drug-induced psychosis, and I can definitely tell that it's not real.

I would say that the clear line between psychosis and genuine psychic ability would be the ability to tell the difference between the hallucination/paranormal experiences and the physical world. That's my opinion, anyway, based on the reading that I've done.