I've never experienced, but I have read on this forum of other people who encountered this. It is like a membrane of the dream as someone described it. I think a part of this is a mental limit you set upon yourself. Because you encounter this you now may (sub)consciously think you can surpass this. But someone else who encountered this 'problem' mentioned pushing through this membrane with sheer will-power and it works to propell you, possibly into/out of the other dream bubble you created for yourself.