Congratulations Casey on the birth of your niece! There is really nothing that can describe looking at your child for the first time but you've come very close. It is especially incredible to see them grow because they really do get bigger and smarter every day and every new discovery brings them joy.
Everything my baby girls did made me laugh out loud, even when they woke me up crying I would go to them with a smile on my face (although that part got old quicker than the rest of it, I must admit).
I grew up with a bunch of college-aged uncles and all of them were great, then as an older kid I got to take care of their kids. Really the best part of my growing up. Have fun with her