6th gear
In my experience flying is all about repetition, so the best way to reduce the nerves is to go back and do it again and keep doing it till you feel comfortable.
I suspect that there are a lot of professionals who have anxiety lurking just under the surface (not me of course
) and while they are in there comfort zone there is no problem, but push them to the edge and it starts to come back, high altitudes being a common one.
I flew an R22 at 8000 feet AGL once or twice and didn't enjoy it at all, but if you did it regularly you would become accustomed very fast, wheras 8000 feet in bigger aircraft feels very normal, this is all new to you so hardly surprising if you are not comfortable.
Just as well your instructor is not TC, with his direct approach