Do not write your text.
Do not even bother writing an outline. Not even the ideas.
Start practising your speech by just saying it out loud. Impromptu. Dont stop. Dont correct yourself. Dont start over. Say the whole speech from the beginning to the end the way you see it now. When you are done, say it one more time. And I mean, say it! Dont just say it in your head, but out loud. Do it a few more times. It doesnt have to be loud, you can be quiet, but you have to say it. Do it a few more times.