What is the most difficult thing when doing a presentation?

Personally, the most difficult problem I face while doing a presentation is the delivery of the information onto an audience. When there is a large group of people present, I seem to always lose my nerve. Seeing as how I am chronically plagued with stage fright, despite continuous practice, relaying a message in a room full of people whether or not they are familiar has always been a challenge. On the other hand, the pitch of my voice too sometimes poses a another challenge which enables the stage fright. Stemming from being overcome with nerves, the tone and volume is sometimes affected which might affect my delivery as well.

These are what trouble me the most when presenting.