Must I memorise a speech completely to sound natural on stage?

Not necessarily. In my experience, trying harder to memorise the entire script can sometimes make speech sound more stiff. Understanding what I want to say, grasping the main points and then expressing them as though talking with someone is more helpful to me.

When entering speech competitions in the past, I tried both memorising a script and working from key points. Memorisation can make listeners hear that you are reciting something. Speaking after understanding the material gave me a steadier presence instead. This does not mean failing to prepare. It means preparing the content without binding every sentence to a script.

Before going on stage, I briefly closed my eyes and took a deep breath to ease my nerves. That was a method I used then, not a guarantee that nervousness would disappear. Relaxation still needs to stay connected with the subject: I have also spoken so casually that I went off topic.

Later, recording podcasts was not fluent from the beginning either. Although I had gained understanding within, when people asked about practice or life I could not always explain deeply. Continuing to experience things and practise sharing gradually made my speech feel closer to people. Natural expression therefore still has understanding and practice behind it.