The reason that it doesn't matter whether you are perfectly complete and orderly is that people aren't going to remember your whole talk. They are going to remember whether you got them interested in the subject--whether you convinced them it matters. They are going to remember the general flow--did it have massive, ugly logical holes, or make confusing references to facts not in evidence?--and one or two facts. And they are going to remember anything you said that was engaging or funny--which you are much more likely to do if you are relaxed and looking at them, than if you are staring at the screen, or the seven sheets of 8.5X11 that you brought.
Here, again is Aristotle:
Of the modes of persuasion furnished by the spoken word there are three kinds. The first kind depends on the personal character of the speaker; the second on putting the audience into a certain frame of mind; the third on the proof, or apparent proof, provided by the words of the speech itself. Persuasion is achieved by the speaker's personal character when the speech is so spoken as to make us think him credible. We believe good men more fully and more readily than others: this is true generally whatever the question is, and absolutely true where exact certainty is impossible and opinions are divided. This kind of persuasion, like the others, should be achieved by what the speaker says, not by what people think of his character before he begins to speak. It is not true, as some writers assume in their treatises on rhetoric, that the personal goodness revealed by the speaker contributes nothing to his power of persuasion; on the contrary, his character may almost be called the most effective means of persuasion he possesses. Secondly, persuasion may come through the hearers, when the speech stirs their emotions. Our judgements when we are pleased and friendly are not the same as when we are pained and hostile. It is towards producing these effects, as we maintain, that present-day writers on rhetoric direct the whole of their efforts. This subject shall be treated in detail when we come to speak of the emotions. Thirdly, persuasion is effected through the speech itself when we have proved a truth or an apparent truth by means of the persuasive arguments suitable to the case in question.