"Some of the routines come back very easily. We do it off the top of our heads"

This quote by Jerry Stiller talks to the power of muscle memory and the ability of the human brain to bear in mind and recall information. It suggests that some of the regimens that he has carried out in the previous come back to him really quickly, which he can do them without having to believe too much about it. This is likely due to the truth that he has done these routines sometimes previously, and his brain has stored the information in his long-lasting memory. This quote likewise speaks with the power of practice and repeating, as it recommends that the more you do something, the easier it ends up being. This is why practice makes perfect, as the more you practice something, the more likely it is that you will be able to do it without having to think excessive about it.