We've all been there. You spent all night going over exactly what to say in your speech, possibly even writing note cards to help you get back on track after losing your flow. Then the big day comes, and you're summoned to the front of the room, with over 10 pairs of eyes all of a sudden looking right at you. The pressure feels so great that you are all of a sudden at a loss for words, all those hours of preparation have suddenly vanished and you have drawn the ultimate blank.
This would be a common case of Stage Fright. While everyone has a different experience with it, the philosophy behind it is simple. The ability to speak in front of groups of people is a very valuable skill. Some of the most highly paid jobs in the world are in Public Relations, where executives have to communicate to the general public through press and other forms of media.
The first thing that you have to realize, to get over your fears of speaking/performing in public, is that practice makes perfect. How does someone get better at doing something? By doing it, of course! If you have a problem with public speaking, there are organizations, such as Toastmasters, that can help you get over your fears by having to give multiple speeches a week on varying topics. If you are in a band, try to get to as many Open Mic Nights, or gigs, as possible to play in front of a larger audience.
The key is repetition. The more you expose yourself to the challenge of public speaking, the greater your confidence will build. You have to realize that speaking and performing in public is an acquired skill, and that to conquering it means that you have to face it.