If you have an important presentation coming up, it's natural for you to be worrying about it. But you shouldn't obsess about it! In fact, the more you dwell upon possible outcomes of your talk, the more likely you are to lead yourself into negative territory.
That's called a "self-fulfilling prophecy."
Of course, thinking this way isn't going to do any good for your upcoming speech. So why not imagine positive outcomes instead of negative ones? Doing so is called practicing a "positive visualization."
I go a step further and label doing this a "Commanding Performance" (as in an award-winning movie).
This isn't a real movie, but a scenario you come up with in your head. Here's how you go about it: You "see" the positive outcome of your speech or presentation beforehand. Then, when you deliver your actual speech, you're much more likely to end up with a beneficial experience rather than a negative one.
Simple, isn't it? Here are some more hints:
Be sure to include all the good things you imagine will occur when you speak: meeting your objectives, an audience that pays attention, people thinking of you the way you want them to, etc. (Since it's in your head, you have perfect license to do so!) Importantly, include how you feel about the situation.
The amount of specifics you include is entirely up to you.
Here is a sample Commanding Performance I've created. The one you come up with will be entirely different, of course. Whatever the reality of your situation, try to make your "movie" as close to the real event as possible (given the details you know beforehand, that is).