My DS is 5 now but the ages of 3 and particularly 4 were very hard. And he's still difficult now. It just seems to be his personality. He's sensitive and not at all easy going. One minute he's sweet and loving. The next he's just feral and rude. I've noticed that proper sleep and nutrition is very important to him. But your DD sleeps a lot longer than him!
So no advice, just that I understand how draining it is!