Nursing as a second career

I've been a Licensed Massage Therapist for 12 years and I left that career to pursue nursing. I received my LPN license in 2011 and worked for almost 2 years in that field. I never felt like a competent nurse, although my fellow nurses and aides all said that I was doing a great job. I felt like there was so much that I didn't know and worried that I would make a life-threatening mistake. This worry translated to me getting diarrhea during every shift. So, I quit and went back to massage therapy. I am currently in a transition program to obtain my ADN. I just wonder if anyone else out there has been where I am and can offer me some words of advice, encouragement, etc. How long does it take to feel confident in your abilities? There were moments that I thought I was really "getting the hang" of this thing called nursing, then all hell would break loose and I felt like a chicken with it's head cut off. Please tell me it gets better with experience.