Mentality has to be strong on this one, like Aaron Fisher said, "You gotta go out there, and keep on swinging". For me though, i rarely shake a lot when i perform to people these days, as before if i know there is more than two people in the group im performing for, i would shake a lot.
Think of it like this, you do magic, for what? If you want to show a fraction of Astonishment then you cant be afriad, or else it wont work. Personally i dont do Magic to Astonish people, i do it because i want people to recognise what value magic has and how far it can go, what it actually is and to respect it properly, because theres a lot to love about magic - and for someone who is chained down to worldly matters each day, they wont get much chance to see any Magic. Astonishment follows on.
So you have to be serious about yourself and your magic, if you take it for what it means (to you and hopefully for everybody), you will improve, or become eager to improve - first step is stepping out of your comfort zone. Once you are serious, then you are ready to take command.
I noticed this when i was performing Yesterday, and i got crowded, my friend who had the camera was like "Okay we getting crowded!!", but it was cool, made me remember myself back in the day when we got kicked out from the same Mall we still perform at. Was performing Overkill at a 90 Degree radius. Didnt shake at all.