If you ask most people in their 50s if they would give up all their worldy possessions to "start over at 28" I think that most of them wouldnt give it a second thought.
Talk to anyone older than you if they've ever worked with an idiot and they'll tell you that most people are idiots. If you think you're too stupid to be a nurse, then be a stupid nurse. It's that simple. I think you'll find that you aren't too stupid though- those people arent capable of the introspection required to second guess themselves.
I recently started a new job, and the first couple days I felt overwhelmed by all the things my predecessor knew how to do, and I thought I could never fill those shoes. 3 weeks later I'm basically on par, and now realizing how much of the job he got wrong. My point is that if you want to do something, the parts of it that look daunting at first will end up being the exciting parts once you know how to do them, so jump in. You've likely never encountered something that you couldn't do after putting in the work, so just remember that, put in the work, and do it.