When I was watching the SpaceX video animation of an ITS mission to Mars and it showed a "fly-through" of the interior of the crew area of the spaceship I was amazed at the large amount of empty space inside, and of course impressed by the huge viewport in the ship's nose ("bow"? "Pointy end"? What is the right term?). I suspect all that open space will help the crew tolerate the months in space that they will have to endure.