The struggle to focus during a yoga class?

Ok so thinking about this blog hasn’t helped my focus much. I need to try being present again. It's so hard! Concentrating very hard on not thinking feels impossible. I get there for a moment, but in my head it sometimes goes something like this….
‘Focus on breathing, listen to the instructions, don't judge my postures, don't compare yourself with anyone else, this backend is uncomfortable, why aren't I progressing, how can she bend back and touch the top of her head on the floor and after 8 years I still can't see the back wall. Calm down at least you made it to class, breathe, visualise a sunset, you'll feel better after class."
My focus this year is to make improvements in my focus, but where to start?….Hmm!