I just had the longest and lucid obe ever ! Funny thing was i kept trying to get out of my body but as soon as i will start it my rest of the body wud come off but it will be stuck at in my head area... And i wud lose consciousness fall bck again in body..
Surprisingly this time it didn end after one try.. I didn wake up in physical again,, so i re tried... Again n again.. I was able to "wake up" to the degree i wasnt able to in past.. Uk bring in more conscious.. That fight is exactly like how u r trying to remain awake in meditation when u r feeling sleepy haha.. So for few times i wud just make my hands go thru nearby wall and my legs n head..
This situation is typical of the beginning OOBE practitioner. It is caused by too much cognition active at the time of the OOBE. What one has to do is develop awareness beyond cognition, then moving in and out of body, and through the immaterial domains becomes second nature.
But i was not able to cross cause this time i felt this extreme blissfull sensation which i have felt earlier, while crossing concrete or matter in general,, but this time it was intense., to the point it felt like jolt of electric bliss..
You will find that if you just focus your attention upon the bliss factors that you will make tremendous progress as a mystic.
So i cudnt make it go thru all the way.. And then at the last it was getting ugly though.. In the last try, i kindof got stuck midway,, ( now only its occuring to.me that it was paralysis state: my mind tried to.panic there and even imagine horrible entities around me but i didn let those thots overcome cause it also occured that its not wise. Cause i have had bad expriences in past for thinking negative? ) it felt like i got stuck in some sheet or layer of water which was not allowing me get out of my body,,, and then i tried to wake up in physical by remembering everything i cud think of hahaha omg it literally felt like i m stuck forever. I even started thinking my people wud make take me.to hospital where my physical body will be lying in coma for idk how long time... And i wud try to recall the sensation of breath, sensation of boundary of physical body.. I was even breathing fast to make physical breath more noticeable.. But i didn realize that time that it wasnt my phsyical breath, but just a lucid sensation... Anyways so after few seconds of extreme efforts.. I kind of accepted it ( my equanimity helped alot,.which have improved alot over past few months, otherwise ik how intense a negative thot can become) so then after a second or so.. I woke up in physical again... But im just curious to knw that does sleep paralysis always ends on its own ? If u happen to get "locked" in it andim even recalling one more such incidence of past, where i felt im.inside my body and somehow my eyeballs r rolled back( that cud be cause i was not able to open my astral eyes) and i wud try again n again.. And it felt like forever and i tried for few mintues and when i stopped trying, i woke up on my own in physical.
In my experience the OOBEs always end on their own, so it is doubtful that anyone could get "stuck" in the immaterial domains, or half in and half out of the body.
With experience you will get more comfortable with the OOBE.
What exactly causes the OOBE? Is it the body being motionless for long periods of time, or the still mind? As when I meditate I move up and down the first 3 jhanas the whole time and nothing happens. 
If you recall the OOBE is the next layer in depth below the 4th jhana. So, for facility with the OOBE one will find mastery to the depth of the 4th makes it all work better. It is otherwise driven by developing consciousness separate from the other cognitive processes.
I shud have mentioned, it happened when i was feeling very sleepy in my meditation so i just laid down n continued meditation.. And then i didn knw when sleep took over and next time when i got conscious it was in astral world (sleep paralysis state). These experiences happen when in meditation u manage to get to a point where body is numb and then u lie down continue like this, u shudnt move ur body and u shud drift into sleep without knwing that u did. I mean if ur too conscious sleep wont happen, and if u give in to thots andd sleep prematurely (in which u consciously give up meditation and choose to sleep) then also sleep paralysis wont happen.
Now that is about going there thru sleep, which is still not the true "yogic" way. Thats what i believe cause this thing u cant repeat at will.
Otherway is going there thru meditation only. Where u dont lose consciousness, thats like how Jhananada says, switiching over from 4th jhana to the transition state, which i experienced in past 2,3 times. So i m not at a stage where i can do it thru Jhanas directly.. Thats why im sticking to my meditation this time and achieve that ability to willfully go there. In my experience, when in meditation the already very faint breath which signifies 4th Jhana , stops effortlessly which will be accompanied by effacing of sense, u can go obe. So like Jeffrey says after reaching in 4th Jhana we cant do much but sit more n more in that state and let next state come. Practice is the only thing we can do.
This is correct, I found that the sleepiness phase in deep meditation tends to precede the OOBE, so early on I took to laying down meditation at this point, which took me right out of the body. So, I find regular lying down meditation it critical for developing the OOBE.