The only thing I would suggest, is to keep the big picture in mind and take care of yourself once you get there.
Grad school was a 180 from my undergrad, and I don't think any advice I heard beforehand made any sense until I actually went through it! I say take care of yourself, but looking back, I didn't have time to eat some days, let alone get sleep, exercise, have normal relationships... It was not really all that bad in retrospect, but a hard experience to anticipate.
So my advice, just take care of yourself. Enjoy the freedom and break you have now, and listen to yourself when you get there. It's a lot of work, and it's not easy... but it's also not really hard per se. It's a whole new skill set you'll be learning, and while I found the coursework easy, it was more a personal growth/journey - and that's what was hardest.
Your experience will be your own, and it sounds like the school you got into thought you were ready. There will be plenty to worry about when you get there - so enjoy life now. Grad school changes life as you know it (but it's great)!