Your child always thinks it's his turn, even when it isn't.
The fix: The ability to share doesn't kick in until around age 4, so don't expect your child to play very fairly before then. But it's smart to introduce the idea of waiting and taking turns now with a simple game of "my turn, your turn," says Dr. Bellando. "If you're feeding your child berries, give him one and say, 'Your turn.' Then feed yourself and say, 'My turn.'" Do the same when you're building a block tower or playing other games.
And if your child refuses to wait his turn? Calmly and firmly explain that he can't use the truck right now because someone else is using it, then distract him with a different toy or activity.