It always wants to ride up the sides of my bed because elastic never wants to hold it in place. When I wash and dry my sheets it inevitably spirals up in the washer and dryer so it never washes or dries properly. Then it’s a pain in the ass to try and fold neatly.
I feel like I’m failing adulthood after being bested by a bedsheet.
Buy nicer sheets and you may need to buy the ones made for a deep mattress.
As a last resort you can buy clip on sheet holders that will make sure they won’t come off, but at some point you’ll probably end up ripping your sheet if you use them.