Your not my mother?

So Koen for the first time is having separation anxiety. When I go to drop him off at the gym Kids Club, I am immediately called back. When I walk through the door there is Koen, hysterical!. With that look on his face like "OMG! MOM! how could you!, you just left me here with these strange people!" He even gives me a mean mug! Good grief!. I know that this is only a phase and one I can't wait to get passed. I looked up some tips on trying to help him get use to being without mom and dad. But if any of you seasoned mom's out there would like to pass on your wisdom, I would gladly take it. I will keep you posted...