'Master Your Instrument for Speed' Question (title edited)

[Ampersnd]

If I may ask out of genuine interest, I'm hitting spells of serious improvement, and then serious nervous system "frustration" at this point, where I play very sloppy, no matter what I try. This can change hourly.

Note that I'm outside in some heat and humidity, so there could be some effect there.

What do you think? (Perhaps a 5G & Magnus musician release could deal with that issue )