3 year old just won't listen

He has been an absolute angel for his Dad (My Other half) all day. His Dad leaves for work and he just won't listen to me. He won't eat his dinner. He's thrown himself on the floor to cry three times. And his dad only left an hour ago! And of course because I'm an hormonal ball of emotions, it reduced me to tears. I've had to raise my voice at him and my throat already hurts because of a stupid cold that's going around, so that didn't help. I didn't realise how much help I actually needed until now, and I can't keep doing this. It's exhausting and I'm already tired enough as it is. How do people do this? Why do people do this? I'm beginning to think I should have stuck with just the one.