Chalk this one up to learning the hard way.
Last month while trying to navigate back from the bathroom, in a hotel room, in the middle of the night, I somehow managed to not quite land squarely on the bed, resulting in a heads-first, blind tumble into a wall, which unfortunately was textured. So in addition to a good bump on the noggin, I ended up with a bit of a bloody mess on my scalp.
The root cause was I couldn't see where I was going and so I bought the box of mini-flashlights shown below, add one to my travel bag to illuminate the way. They're plenty bright enough for a middle-of-the-night bathroom trip, but not so bright as to stir a sleeping wife.
Perhaps a Christmas stocking stuffer for someone you love?