Artist and SkiBum,
Let me addle the waters a bit.
When racing MX I've had days that everything felt off; timing, balance, coordination, bike control, etc. only to find out I'd just put in my fastest *ever* lap time. Other days feel smooth, in control, with slow or regular results.
I've had the same experience riding street; apexes aren't where they should be, braking too hard with resultant nose dive, the rear stepping out, the bike being twitchy, and apparent misjudging of cornering speed. Never out of control, drifting the lane, or running wide into the mountain, but just feeling 'awkward' - only to find I've left my best and fastest riding partner behind on a section he routinely cleans mine (and everyone else's) clock.
Interestingly enough, the symptoms Artist describes are very similar to ones that *sometimes* describe riding at, for me, advanced performance levels.
Then again there are times where I have simply pulled off the track or rode 'quietly' home because the day was just too 'off'.
Hope this makes no sense to you at all, otherwise you too have the curse.