When you sprain your ankle, DON'T MOVE. I used to try and walk it off because that's what everyone does and even coaches recommend it, but that's when the actual damage is done.

Spraining is usually just your tendons/ligaments going into emergency mode (getting very short/tight). So if you try to walk while they are still tight, they will actually tear, doing damage that takes weeks to heal. If you instead just keep that ankle perfectly still for like 30 seconds to 2 min, the ankle will be completely fine.

Trick is, you have to overcome the social pressure to hurry it along (i.e. on a hike at work, or on a sport field).