You make your bed with the best of intentions, but tossing and turning throughout the night can pull a loose top sheet into strange and tangled positions. If you want to keep it in the right place, redditor Midgers suggests making a knot or two.
Tie a knot at the end of your flat sheet and tuck it into the fitted sheet. It won't come loose during the night. I discovered this while searching for a solution to bunched up flat sheets in the morning as my boyfriend is very tall and very fond of kicking them untucked. It works like a charm and they always stay put.
I've always tucked mine under the mattress, but I manage to eventually untuck it after 1-2 weeks. That said, if you want a reminder to wash your sheets at a regular interval, you could just do it every time your top sheet comes untucked.