If you are organized and did well in your BSN, you'll do fine with your MS/DNP. As previously mentioned, you may have to read a great deal and reread some topics to get it into your brain.
Not having practical experience as an RN means you may not quite understand the dynamics behind some problems/diagnosis/acuity and lack that "gut" feeling gained from working in an ICU/ED/unit, etc. Many NPs worked in a clinical setting before attending grad school. They have a "working" knowledge of many concepts. Now, your situation is not a bad thing, I'm not trying to be negative, but just to understand that your anxiety is perfectly normal as you don't have the experience of some of your peers that may seem more relaxed and confident.
It's one thing to graduate, pass the NCLEX and jump right into a NP program, quite another to have a few years in your pocket (might have already pumped a chest a few times, inserted PIVs/pushed cardiogenics, delivered a few kids or assisted with hundreds of surgeries). As a seasoned RN, you have the benefit of watching providers and learning how they think/act/perform and the outcomes, both positive and negative.
One concept you are going to learn in clinicals, the book is not always "black and white." Read the chapter on cough/cold/flu and you see nothing about Warfarin. Which antibiotic are you going to Rx and why? Non-healing diabetic wound/ulcer, what's the best approach to the wound...likely not in the book, but most RNs have cared for these patients and can chime in on what works best. Crutch walking, catheters, trachs/ostomy, so many concepts that you learn while working as an RN, that will not be touched in grad school. This is why many BSN instructors will push you to get a year or two under your belt before taking the leap into grad school. Not required by any means, but definitely most helpful.
I would further recommend at least some part-time work (if you can find it) to learn some of these helpful concepts. You'd be surprised how it will help build your confidence. Congratulations and best of luck, BTW...which specialty are you planning?