In Day and Night when you are playing Day mystify rarely seems to be useful. Towards the start of the game time spent attempting to mystify squares will either be wasted when night swiftly reverses them, or gain you a square which doesn't end up being important.
Towards the end of the game, time spent trying to mystify a couple of key locations to force a win often results in night overwhelming you with quick tile turn-overs to gain their second temple, when it would have been better for you to simply concentrate on turning over night's tiles to prevent this directly.
