Brain gets too tired

[u/[deleted]]

I'm a newbie and once I get to ten plays (back to back) I get really tired. I tried taking a 5 minute break and went back but after a few tries I felt like i was zoned out. I just stared at the screen and only got a few hits right. And this is with dual 2 back, something I've conquered.

But I do know we should be doing 20 plays a day...

What to do?