I've never subscribed to the idea that you should try to miss on purpose on a shot you want to make, and I never will. Shoot to the thin side of the pocket, sure, but try to miss, on the odd chance you could make it...NO, hell no, never!
I think some of the reason why a good number of older pool players get worse as they age, before their eyes go or other legitimate problems occur, is thinking like this. "Cinching" shots by shooting a speed that will give you a hard next shot (to ensure the make), shooting to miss, playing too many safeties, playing weak safeties.. You can be as smart as you want, but you have to make the shots. As Efren once said to Strickland after Earl lost and whined about luck, "You don't make the shots, how can you win?".
Look, this game is about winning. When playing weak players they will give the victory to you. Playing good players you have to grab the victory by the throat yourself. You can't fiddle around like this, or you'll either stay an APA 5 forever or become one by going backwards.
Rant end.