I went to nursing school back in 1973 having absolutely no experience as anything but an account clerk. I used to get nauseated and almost throw up every time I pulled into the parking lot and started walking into the hospital to do my clinicals when I was in nursing school. Not only was I afraid of the same things as you, but I was scared to death that I would accidentally kill somebody! This fear was with me probably for a good two or three years AFTER I graduated from nursing school as well. And, then, at some point I had seen about as much blood and gore as I guess my mind was able to process and put into perspective. I realized that I wasn't going to kill anyone. It will happen to you too.
The worst, for me, was not the blood and the poop, which is what I kind of expected. It was seeing little bits of a person's gray matter (their brains) on their pillow case after they had tried to blow their brains out. It was the only time I nearly barfed. To this day, I still don't understand why I had that reaction--and it's happened to me twice. I've seen arterial blood spurt across a room after an artery was accidentally punctured (the seriousness of it aside, it was actually kind of cool!) and patients have explosive diarrhea or vomit that landed on other nurses (they got to take quick showers and put on clean scrubs
down in the OR). It's kind of like a rite of passage that makes you one of the gang. Everyone loves to talk about their "war" stories.
I imagine that you're going to be just fine. First of all, your instructors aren't going to let you do any procedure until you've been checked off on it in the lab at school. The instructor stays with you the entire time you do a procedure on a patient to make sure you're not doing anything wrong or accidentally hurting the patient. I was never allowed to start IVs as a student. It just wasn't allowed in my state. Once on the job I turned out to be a terrible IV starter. I was so bad at it that I took the 30 hour course given to LVNs here in California. I kept working at it and eventually did get very good at it and ended up working on an IV team and putting in PICC (peripherally inserted central catheter) lines as well as being nationally certified.
As for thinking you might not be smart enough to do this. . .I used to tell myself that if thousands before me could get through the training, so could I. After all, how different was I from them? I'm just a person. You're just a person. You can do this too. I guarantee you that just about every nurse went through the same fears when they started nursing school. You are not alone.
Good luck! See you on the forums! Welcome to allnurses!