Stress.

There are many ways to deal with stress. It is as simple as that; some people however, refuse to take the easy way out and make situations more stressful than necessary. Stress can be managed in very simple ways starting with this:
Write down what scares you most:
Often pressure and stress arise from situations where you can easily fail. By writing out the things that scare you most about your stress, you release them from your brain.
Embrace the Silence:
Use times in your presentation when you forget to simply collect your thoughts, there is no need to constantly fill every single silent moment in your presentation with meaningless chatter.
Meditate:
Relax! Realize that although this stress is a big problem now, it might not matter tomorrow or the week after that. Take time to be quiet and think through your fears.
Lastly: Separate what you can fix and what you cannot fix:
Learn to tell the difference between things you can control and things you cannot control. What are variables that you can positively influence and what are things that are over your head, and out of your control?

Learning to positively control your stress levels brings a sense of relaxation to every situation. The most important part of stress is to remember that everybody suffers from pressure and pressure is nothing more than opportunity.