Im not sure why it is, but if we are asked to stand up in front of other people and speak, sing, play or dance we often have some sort of melt down.
Its been called stage fright and I have certainly had clients who said they would rather have teeth pulled than stand up and give the best man speech!
Thing is, everyone has those feelings. Its how you process them that's important. If you love what you do or you want to show appreciation to a friend in the best man speech scenario, then maybe you can process this as excitement and not fear.The brain loves excitement, just think of all those fairground rides and bungee jumping. Speaking or performing in public is virtual bungee jumping- an adrenaline rush.
Your audience want you to do well and are mostly rooting for you. So, breathe, take in the excitement and then sing, dance, speak and play your heart out!