Do you do other exercises besides ITG? If so, on the days you don't play, jog around your nearest park. Get some cardio back. Your accuracy will come naturally with comfort, and comfort will come with increased stamina. It might help to drink water instead of soda for a while. If you want, eat hearty meals before you play, as you'll have something to burn. Stretch out.
Also, warm-up to some hard 10's that have little stream, such as Max Forever, as that'll get your stamina pumping for later songs.
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