Lucid Dream Experiences

I have a book about it called “Experiences Beyond the Body” which tells stories about astral projection and also has some exercises and teaches you how to do it.
I’ve never been able to successfully project, although I first heard of it 15 years or so ago and have gone through periods where I would try for a while. Here are my experiences:
When I was younger I used to have lucid dreams from time to time. They were awesome and I loved them. I didn’t know what they were at the time, however.
Later on as a teenager I got more interested in this stuff. Of course, as a teenager, as soon as you become lucid in a dream you turn it into a sex dream. Don’t laugh, you know it’s true! You probably still do it, too, even as an adult. Anyway, the lucid dreams became less and less frequent. At this point, when I became lucid, it was a struggle to not become excited and wake myself up. That’s a common problem, too; as soon as you realize you’re lucid you wake yourself up.
I learned some tricks to prolong the dreams. If you are lucid and feel yourself starting to wake up, there are some techniques you can do in dream to help keep yourself dreaming. The two that I tried were 1) demanding “clarity now!” in your dream. Think it. Say it. Make it your sole intention. Sometimes it works, sometimes it works momentarily and you still wake up, and sometimes it doesn’t work. 2) spin around. Seriously. Whatever you are doing in your dream, just start spinning. Sometimes it works, and sometimes not. But if you know you’re about to wake up anyway you might as well try it. There are more techniques which you can find by Googling.
Sometimes I would experience what is referred to as partial lucidity. It’s when you kind of know you’re dreaming, but you’re either not 100% aware, or you are aware but cannot fully take control of it. It’s like your mind is working against you.
Sometimes, usually in the morning like if I wake up but stay in bed, I would get that “falling” sensation. I have heard that this can be a predecessor of an astral projection, so I would try to work with it. Sometimes I can feel myself kind of floating in my room, but I can’t see anything. Sometimes I end up dreaming in this state. Sometimes I end up dreaming that I am in my room, perhaps what I am imagining an astral projection would be like.
I have also had a similar thing happen at night, where I feel like I am floating, but it’s a scary, uncomfortable feeling. And usually I can’t see anything.
I have also felt the vibrations and heard some strange rushing noises, which they say are precursors to astral projection, but sometimes they kind of freak me out and I snap out of it, and other times they just fade away.
There seem to be two schools of thought about what causes this.
1) it’s something metaphysical
2) it’s just something going on in your brain
People who think it’s just something in your brain also tend to dismiss near death experiences (NDEs) as just the brain shutting down. There are also reports of people experiencing NDEs from stimulation to certain areas of the brain. However, I read something suggesting that perhaps in those cases, the stimulation was triggering the natural events that happen when you die: sort of “hacking” the brain. So yes, it might be caused by electrical stimulation in a lab, but it’s an actual process that is being activated (although obviously not to completion since the person didn’t die).