Why do we worry?
Because we care.
I remember after the birth of my first child. I felt guilty at the amount of anxiety and fear I felt rush over me the day he was born. A close friend put it in perspective by saying "what should really upset you would've been not feeling worried and afraid." What he meant was that those feelings showed that I understood it was a big deal and I knew that life was about to change.
I'm still worried and anxious about tomorrow, even though I've done this more times than I care to mention. It's the first day of school, and it's a big deal for my students, for my parents, and because of that...
...it's a big deal for me.
I'm sure it's going to go well. But I'm still worried. And I wouldn't want to be any other way right now.