The risk of physical danger depends mostly on where you’re doing the majority of your performing. If you’re mainly a stage actor, about the worst that can happen is you run into a set piece in the wings or get so into character that you accidentally walk clear off the edge of the proscenium. More physical danger exists in the world of film, where the physical demands can be more strenuous, especially if they’ve got you doing stunts. Really, the most physical danger comes from breaking your toe and not having health insurance. You may find yourself walking around on that waggly stub for a while. Of course, if you decide to go the stuntman route, then you risk becoming a mangled mess on a daily basis. And there are plenty of dangerous temptations associated with the biz as well–everything from alcohol to drugs to advanced planking. Avoid them. Especially the planking. No good can come of it.