Cotton pillowcases cause friction, leading to breakage and frizz. Swap to silk...

https://gunnerawsh736.cavandoragh.org/sleeping-your-way-to-stronger-strands-the-ultimate-guide-to-overnight-hair-care

Cotton pillowcases cause friction, leading to breakage and frizz. Swap to silk for a smoother surface, or braid your hair into a loose, low plait before bed. It’s an easy habit that keeps your hair healthy and makes your morning routine much simpler.