Since reading the book Why We Sleep: The New Science of Sleep and Dreams I tried to find ways to improve my sleep quality e.g. #66: 2h No Screen Time Before Bed. The last experiment I did was just trying to sleep without a pillow. The first thing to mention is that sleeping without pillow is recommended it you sleep on your back, so I needed to build a habit first because I was a side sleeper. After around a month my overall sleep quality improved.