So, my baby starts preschool tomorrow. He's 3 years old- I'm a nervous wreck!! I'm so excited, But…

So, my baby starts preschool tomorrow. He's 3 years old- I'm a nervous wreck!! I'm so excited, But at the same time, im just so nervous. What if he hates it?? What if he cries for me all day?? (I do have separation anxiety with him... And I hate being away from him) I know its only 4 hours, but I need positive words! Please and thank you!!