To manage anxiety, start with the way you think
Get past your own thoughts
Fear is largely caused by your thoughts. Your body gives you a fear stimulus and your mind takes off, giving you all kinds of irrational reasons you should be scared.
Of course the reasons aren't always logical — you aren't going to make a complete fool of yourself if you have to make a speech — but these irrational thoughts fill your mind and intensify your fear.
Don't believe them!
Instead, identify those thoughts that are causing you fear. Challenge them. What evidence is there you'll make a complete fool of yourself? None. You might not receive a standing ovation, but that is OK, your goal is to give a professional presentation where your audience can learn from you. Reappraise the situation and distance yourself from overly critical thoughts.
How you think about a circumstance impacts how you feel about it. Approaching your fear rationally, realistically and changing how you think will help you overcome its strong irrational stimuli.