(Management is not responsible for resulting musical theater addictions. If your earworm lasts longer than 24 hours, seek medical treatment or listen to something else real loud.)
Anyway, this is really good advice for our current stage of parenting.
Especially when you're giving instructions. Yes, kids this age can understand and follow multi-step directions. But they need some processing time to do it.
Furthermore, when tantrums are happening, interaction prolongs them. As long as there's an argument to be had, the kid will reflexively continue having the argument. Make your point concisely once, then stop. Eventually the flailing will burn itself out. But every time you say something (or, in M's case, try to touch her -- I hear some kids like being held when they're upset, but NOT THIS ONE) you reset the clock.
Example from this morning: Morgan is chewing on the edge of a box of Go Fish cards.
Aaron Burr: If you put cardboard in your mouth it will get wet and the box won't hold the cards anymore. ::waits for child to process information and come to conclusion that she should probably take the box out of her mouth; or not, honestly, no particular skin off my nose either way::
Alexander Hamilton: Morgan! Stop chewing on the box! It'll get all wet and the cardboard will fall apart and then it won't hold the cards in! Then you won't have a box and the cards will get lost! So you should stop chewing on that right now! Or the box will break! Morgan! Stop chewing!
Two points: One, if you can think of a way to make it a game, make it a game.
Example from yesterday: Morgan is scared of the doctor and doesn't want to lie down so he can check her tummy. She has brought a stuffed animal along to keep her company.
Aaron Burr: Do you want Figment?
Aaron Burr: Here he comes! Oh no! He's jumped on you and knocked you over! ::gently tilts M backwards onto the exam table::
Two, praise is magic. Catching kids being good and thanking them for behaving nicely or being considerate or doing their chores promptly makes everybody happy.
Don't let them know what you're against or what you're for.
Okay, for this to be parenting advice you have to interpret it a bit differently than it's meant in the song. But I find it helpful to keep in mind during tantrums that I don't need to argue her into my position. As the parent I have all the power; I have already made the decision; I am waiting for her to accept it or emotionally process the disappointment or whatever, but I don't need her to agree with me. (I am in fact totally happy to have discussions about what the rules ought to be at some other time, when everyone is calm and capable of discussing them and bringing up relevant points, but not when there is already upset happening.)
Also, it helps a lot to be able to present choices you are more or less indifferent between. Either you get your shoes on and your dishes put away by X time and we'll go do Y fun thing, or you don't and we'll stay home. If your room is picked up you can have iPad time, otherwise find something else to do. It's much easier on me having a plan for either way things could go; otherwise I am standing there banging my head against a brick wall trying to figure out why the child does not want to do some ridiculously simple thing and is blocking the whole rest of the day. Obviously I usually have a preference here, and I don't generally mind telling her that I am sad that, say, she wouldn't get dressed so we have run out of time to go to the zoo this morning, but the more I practice non-attachment to my vision of how the day will go, the better the day in fact usually goes.
Furthermore, kids this age are practicing differentiating themselves from their parents. That means that they have fairly recently realized that they are independent entities, and just because you told them to do something doesn't mean they have to do it. So direct instructions will tend to invite "No!" or ignoring you or otherwise experimenting with Not Doing What Parents Say, while information that reminds them what they're supposed to be doing without actually being an instruction doesn't trigger that reflex.
Example from this morning: Morgan requests help picking up a pile of stuff on the kitchen counter.
Alexander Hamilton: Okay, start with these hair clips. Your hair stuff box is over on the table by the comfy chair, so go put the clips in there and then put the box away where it goes, then come back and get the next thing.
Morgan plays with the clips while Alexander Hamilton puts away the bag they were in.
Alexander Hamilton: Morgan, are you going to put the clips away? Put the clips in the box and put the box away, it'll just take a minute.
Morgan: You do it!
Later, Morgan again requests help picking up.
Aaron Burr: Okay... I see some shoes and a pair of pajamas in the bathroom.
Morgan picks up the pajamas and puts them in the hamper, then returns for the shoes.