Eve of the 4th year

Micah turns 4 tomorrow... I can't believe it...  I can honestly say since he started preschool 4 weeks ago he really has turned a leaf.  When I respond to his question and say, "no" instead of whining he says, "I don't mind."  And his preschool teacher told me that he told another kid, "if you are mean to people, I won't play with you."  Micah has started writing his name independently, he knows his letters and sounds, and his drawings are really improving... my baby is almost 4.  Where has the time gone???