It’s natural to be a little anxious or nervous before your big presentation and certainly preparation, planning and practice beforehand will help.
(Prior preparation and planning prevents p!ss poor performance). However if you still beel nevous before the presentation, here are some tips.

This one comes from the Royal Shakespeare Company.

Start rehearsing  your preparation, at the same time circling both arms backwards.

Notice how your speech slows down and becomes more deliberate. This is an exercise RSC does when rehearsing lines before the performance.

If you find your mind  and voice are racing away during your presentation, you obviously can’t start waving your arms around, because you’ll attract unwanted attention to say the least. What you can do is to twirl a real or imaginary ring anticlockwise, surreptitiously.

Exercise (alternate finger and thumb)

This is an NLP exercise to remove a mood state. Because you are simultaneously using the left and right side of your brain, it’s virtually impossible to hold an emotion, including nervousness.