Practice helps!

What also helped me is being so knowledgeable about the topic that I didn't need to prepare the presentation much (except for the slides and the general plan). When you know what you have to talk about, it becomes a lot more natural and relaxed for me.

I would be a lot more stressed if I had to learn a presentation by heart and it would probably be a robotic delivery.

So I did quite a few "surprise" presentations, with very light prepared material and a topic I cared about. Got me the practice I needed and I learned not to get "stuck" as if I forgot the next sentence. The presentation always flows!

Now, I have a talk at a major conference, and I'm afraid this won't work there, so I'll prepare my talk better this time, maybe even have speaker notes!