You are an EXCELLENT nurse, or you wouldn't stress about these things.
You have a lot of life experience under your belt; your nursing experience has yet to catch up. It takes a while---and I mean years
---to feel competent in this field, and you've just gotten your feet wet. I know how hard it is not to run yourself down, you tend to think (like I did when I was new) that because you're x-number of years old, that you should have this thing nailed. It doesn't work that way!
Have a glass of wine, a nice long soak in the tub, maybe put some good mood music in the CD player, and relax. Tomorrow is another day, and with it comes an opportunity to learn and grow. Take care.