hi Dr. My son is 3.5 years old. Whenever his cousins(same age and 1 year older to him) come to meet us, the first day he plays and is so happy to see them, even shares his toys. From the next day onwards, he starts crying for his toys, doesn't share and play, and cries for all his things be it books, toys etc. He for no reason pushes them even if they are not playing with his toys.. we always interrupt a no. Of times by saying no hitting and pushing, but he doesn't understand..he himself says no hitting and pushing but doesn't behave like that.. any advice here please. Another thing is that he has a very bad habit of banging his hands and head if he doesn't get anything he wants, a little "no" sometimes make him behave this way. How to stop this?