Communication in teaching movement (or anything really) has two main phases:
Phase one: instruction from the teacher to your ears. Phase two: from your ears and brain to your body.
How does this message get from your brain to your body? If you understand what has been said and what was asked, do you expect to be able to immediately do it on the first try?
Even if your teacher manages to give you excellent instruction that you understand perfectly in your brain, can you instruct your body to do it?
Can you feel the parts of your body you're being asked to move? Do you know how to instruct them?
There needs to be a process of upgrading your ‘software’ before you can follow the instructions. Much of learning is about upgrading this software to translate instructions from the teacher, through your brain and into your body.
Pay attention to this next time you're learning anything. Try to learn what your teacher teaches, while also taking the time to upgrade your software to make it a little easier to learn next time.