Problem: Shaky hands, Nervous, Fear of Failure
Solution:
Warm up your hands get blood flowing. Nothing like cold finger tips to give your routine speed bumps. Do this regardless of weather.
So you're nervous. It's fine. Stage fright is natural. Can you perform fine in front of your family, mirror, friends? If you can't, practice more. If you can, then its an approach issue. Can you perform fine if its one person? What about 2 people? Is there a certain number 8+ that gets you a little shaky? If you perform magic fine and it IS an approach issue, then this has nothing to do at all about cards. Sounds awkward, but awkwardness is what you're fighting. Approach random people and make a point to meet a new person everyday. Soon being with people, strangers or not, crowds or small groups will not be a problem, and the only thing left will be how well your performance skills will be (no nervousness to cripple you then). It will also help you gain a stronger more charismatic personality that is great for performing and will help you build stronger relationships. (Because that's what magic is about right?)
Being afraid of failure should be eliminated by your practice, and your ability to accommodate a set. If you KNOW you can do the trick, there should be no reason to fail, leaving only the people as your variables. If you DO mess up, knowing how to make a joke or how to incorporate things on the fly will help save face, as well as making your "failure" a piece of comic relief. No ones perfect. Chill out. Enjoy magic.