How to keep going even when you're mentally and physically exhausted?

by Aashir Zaidi
(Sydney)

I'm 16, I'm relatively unfit, and I have asthma. I get tired during our two-hour intense practice, which causes me to become sloppy and make a lot of mistakes, and I'm worried that these will become bad habits. I'm not sure how to keep going despite my exhaustion without becoming sloppy and using the incorrect techniques.