Maximize the quality of your bedroom air. Dust, dustmites, mold, solvents from paint or furniture etc. can cause breathing problems which reduce quality of sleep. And most of the time it goes unnoticed because, well, you're sleeping! Vacuuming often, airing and exposing the beddings to UV rays helps. I'm also looking into plants that increase quality of indoor air - see
this TED video on the topic.