Hey i know how you feel!!
My 2 yr old dd started pre-school last week, and she is going two mornings a week. I was supposed to be staying with her to settle her, but the staff told me to go as she seemed so happy. The second day, she wandered in and waved bye without a tear.
The days before i was worrying, feeling guilty about leaving her. But honestly she was so happy there, and it is such a short period of time i enjoyed the peace to be honest with you!
Wish you luck!!