Open Question: I'm afraid of messing up my client and making things worse?

Right now I am in college for a job that has the potential to cause to cause serious harm to my clients. There is so much to memorize and know. My question is does the anxiety and stress of knowing messing up could harm the person and that you could actually make things worse does that ever go away? Also especially when you first get out of school you know there is people better than you out there that could do it much better than you does that fear go away?