It's a lot more doable than you think. Easier, I'd say. Especially, if you're not seriously thinking about and dead-set on specializing. That will require more work (you're kind of back to the beginning where you have to build an application - ECs, research, grades, working the letter circuit, whatever it takes to be competitive). You aren't around a bunch of pre-dents and counselors that don't really know what they're talking about. You've arrived at this destination you've been dreaming/agonizing about for years. Then you're a part of a family. All of you are in the same boat. Only this group of people knows exactly what you're going through in life. This small family for four years. You have all the support and structure you need to get through it. And there is all sorts of stuff going on to balance out the hard work. I'm still kind of shocked at how much people have time to do. Maybe it's just Midwestern, but there's a ton of fun going on all the time. Very few schools out there are still following an oppressive, boot-camp sort of curriculum. It won't be easy in that you won't have to study or put your time in the lab and patients can be a pain in the [whatever body part you want to put here]. But it's the whole atmosphere that is totally unique and what makes it a different kind of stress, that I think is more palatable than undergrad environments.
The stress and nerves now are almost a good thing. It keeps you focused on the goal and working hard on grades and ECs and stuff. Look around and you'll see plenty of proof of what a sub-par GPA can do to your doors of opportunity: they are narrow, delayed, and sometimes closed. Focus on that one thing (and eventually the DAT) more than anything. I know we all want admissions to be holistic, but it's not there yet. It's still a grades game. If you have the time and capacity, take on some ECs that you enjoy! Dental-related or not. Don't kill yourself over this. There are pre-dents who will drive themselves into the ground by thinking they need every section/space on the application filled out. They take on research they hate and put in tons of unproductive hours of useless volunteering they don't like because it's what they think admissions will like. Silly.
Just keep chugging along. Everyone had the same feeling at some point. But when you get there, it's a different world, and you'll be just fine.