I'm concerned that a failure will greatly hurt the progress of spaceflight and the public opinion of it. Other than that.. well, we got 8 billion people laying around, all of us are going to die, and there are very few more glorious ways to do it than spaceflight.
I would be terrified. That being said, I get nervous every time an airplane takes off even though I know that hundreds of planes have safely flown that same day. I can’t imagine being one of the first people to fly in any vessel, let alone a space bound rocket.
Not to mention, the first crewed vehicle to leave Earth's orbit since 1972. Not only do we have little experience doing it, it hasn't been done in nearly half a century.