Are you worried because you want to perform great at your defense of the dissertation? Do you need to improve your communication skills to present your ideas effectively? Do you have enough information about the subject but not confident about the defense? Are you nervous to face the official committee members and other audience at the university? Did you consider practicing in the hall before the final day? Do you want to impress your audience with a great presentation? Are you having a hard time in creating your power point presentation? Do you want to score well in your paper? Is everything else about your presentation ready but not sure about the acknowledgements section?
First thing you need to remember is that if the rest of your preparation is complete and you only need to address the acknowledgement then you are more than half way through your presentation. You do not have to worry only because one small section of your paper is not complete. It is true that all sections in your paper need proper attention because the qualification level is critical. You will not receive your degree unless the official committee approves your dissertation. Keep in mind that each word in your paper should be spell checked and error free. Do not ignore the typos, jargons or any other minor details in your paper.