For about 6 months before my son was diagnosed (age 2.5) he was completely out of control. He would get incredibly anxious about really weird things, about anything that changed, would scream and shout and ignore me and throw things and then sob inconsolably. Everyone said it was just "the terrible twos"...I kept saying it wasn't like him, like his core personality, but then I only have the one child and lacked confidence when faced with "experienced" parents. As soon as he received the insulin, this behaviour stopped and now only appears when he is high, and when he is low he becomes moody and distracted. What I try and say to him is "do you think you can manage this now" and he tries to. I tell him what is not ok (eg violence, mistreatment) and I try to remember that for the rest, I am the adult and he is the little child, who to be honest, has every reason to be pi**ed off and angry with his lot at the moment. I just try and get him to express it without hurting or throwing it onto someone else (me!). And as he grows up, I will try and teach him ways to manage the mood swings that come with the diabetes, just like all the rest.
Somedays I manage all this. Other days I react. And if I am fallible, so is he! I am trying to trust my child. If the behaviour seems out of character, chances are it is either caused by a physical thing, or by the emotional stress of stuff. He can feel what he feels. How he expresses that in ways that do not disrespect otheres is something he has to learn. After all, a lot of adults are still learning that one. And as for others, I try to tell inlaws etc what the behaviour can be, but it is a long journey...