What is the #1 thing that you will or do miss after graduating from middle, kindergarten, pre-k, elementary, and high school?

We all have that one regret of graduating from different levels of education, especially when you were young and missed how it was before you finished your education. Mine was Kindergarten or pre-k cause of how calm and a bit relaxing it was being little. I miss those moments now that I'm soon to be graduating from high school.