joe b. nailed it. :)
For several years in my early career, I worked the night shift: 11 PM to 7 AM. Since most of my friends were from work, we all just kept the same hours on the weekend too. To this day, I have no problems sleeping under most conditions. I've even slept under the #3 arresting gear wire on a carrier.
But the hubby is a much lighter sleeper. I fitted our little RV with the stuff mentioned by Alaska RVer earlier, the silvery bubble wrap stuff. It doesn't get totally dark, as there are light sources I can't block, but it's good enough for him to sleep.