Absolutely!!!
I've definitely already entered imposter-syndrome-mode and am fretting about whether or not I'll be able to hack it, if I'll be able to be the kind of student they're expecting me to be, and so on. But just as someone above said... we managed to get in despite steep competition. That absolutely means something... we're heading into this crazy new world for a reason, we totally deserve to be there, and I trust that we'll surprise ourselves with our accomplishments and abilities. That (or a shortened version of it!) will be my mantra for the next handful of months...
I'm also moving 1500+ miles away from my family, to a part of the country I have zero familiarity with, so that's definitely anxiety-producing. But I'm headed to my top choice school and I'm beyond ecstatic to discover all of the research awesome that will result from working with my fabulous new mentor. Despite any hesitation about leaving my family behind, I know that, while challenging, this is going to be an absolutely amazing journey. Terrifying and overwhelming? You betcha. But what's better than jumping into a brand new life where you get to be immersed in the subject you're most passionate about? I'm really, really scared but also SO excited to see where this takes me....