I cried for the first month dropping my two-year-old son at his preschool and it became a daily battle where I had to stay strong so he could stay strong.
Tearful, tantrum-filled goodbyes are common during these early years and even infants develop separation anxiety if a parent tries to leave them with someone else. Personally, one of the worst mistakes I made was “sneaking away”, thinking that my son would just forget about me as he was enthralled with his new surroundings. This actually made his separation anxiety worse, because he couldn’t trust that I wouldn’t disappear again. He spent 3 months following me around saying “mama?”, I was on a short leash!
The best personal advice I can give is to make a short consistent goodbye routine before they get out of the car (or to the door), remind them that Mommy and Daddy always come back, and tell them (with confidence) to enjoy their day! You can then drive to the nearest coffee house and ball your eyes out like I did.
Whether it’s daycare or preschool I have found two great articles that give solid tips on dealing with the mutual separation anxiety of dropping off your child on their first day.