A true story. In 2001, my ex-collegiate player buddy and I were beating balls at Hank Haney's Golf(Goat) Ranch in Dallas. I was hitting everything flush from 9 to driver. Then my buddy tells me I'm past horizontal at the top. So, I start "stopping and looking", and sure enough, it was well short of parallel. But, the damage was done, and I started trying to feel where the shaft was at the top during the swing. Couldn't hit a decent shot the rest of the day.