It might be the methods you are using. Some have the ability to interfere with sleep (because sleep is needed to leave the body). Or, it could also be that you are simply not spending enough time. I don't want to give you an estimate on how long it takes, because then you might do it too short following my estimate.
This might help:
http://www.astralpulse.com/forums/viewtopic.php?p=193568&highlight=#193568
This might help:
http://www.astralpulse.com/forums/viewtopic.php?p=193568&highlight=#193568