Do not hesitate to preview bits of your presentation in advance with colleagues, supervisors, and others in the workplace who might be interested.
Say, “Tomorrow, I am going to be giving a presentation on [topic of presentation].” Then test one or more of the high level message concepts (redacting any confidential information.) For example, “I am going to be giving a presentation tomorrow on how to give a great business presentation. The ability to present well to a group is one of the most important skills you can have in business and I am going to share the method and techniques I have developed over the course of my career to reach audiences, transform their thinking, and move them to action.”
This gives you the opportunity to pre-test parts your message and you get a little practice in front of real people without giving everything away.
Parts of your message may sound good. Other parts may sound a little rough and need to be tweaked.
Don’t ask “what do you think?” But pay close attention to any reactions you get, encouraging or otherwise as you speak.
Once you have previewed some the material in this way, you will be more comfortable during the actual presentation. Some of the concepts will have been already “road tested”.