A nice trick is to leave the bathroom light on at night and leave the bathroom door slightly ajar or completely open. It depends on how much light you want. This gives you enough light to see inside the cabin but not too much to disturb your sleep.
I have a balance problem where I fall flat on my rear end if I am in total darkness so I have used this trick and also have left the TV on with the sound off to provide light.
If you have some light I don't think you will have any problem with claustrophobia.
Like Pamda, I also think there is nothing more condusive to sleep than the rocking of the ship.
Have a wonderful cruise.
Monday Chat Host and owner of a Mickey Mouse Night Light.