A core reason that people fear public speaking is that they're scared of screwing up and thus looking foolish.
That fear is valid if you're trying to be "perfect"--scripting and when near-memorizing. You're bound to get thrown off.
Fortunately, unless you're a master at reading off a teleprompter,
the best talks are not scripted, nor memorized. They're given largely
ad-lib, with just a brief outline to keep you on track.
I offer a step-by-step process in my PsychologyToday.com article today.