How to calm nerves before lesson?

at my barn theres 2 trainers, mine and another one that knows me and my horse fairly well. today i'm having a lesson with the one i dont usually ride with and i'm afraid shes gonna push me and my horse too hard. whenever i'm riding on my own she tells me to go faster until my horse is working off her hind end but that isnt comfortable for either of us (she is a 6 yr old with arthritis in her hocks) i want to listen to her and have a good lesson without having o ask her to let me go slower or take a break or anything like that. i just want some tips on how to not be nervous... its to the point that i feel queasy!! thabks so much