How can i achieve being calm ??

How can i achieve being calm ?? So a little bit of context, in less than 2 days i have a very important ORAL presentation, so i wanna know how i can be relaxed while presenting. It is very strange because i couldnt care less about what others think of me, despite that, i get extremely nervous, it is something involuntary, like my body enters in some kind of defense mode lol. (I think this has something to do with the “fight or flight response”) I have read a lot in this community and others, that MDMA helps a lot with fluency in stutterers, so im planning to take some before the fucking presentation. So i would appreciate a lot if some of you tell me how i can be more relaxed, and also experiences with MDMA please.