We seem to have dodged that phrase so far. At three, her goto was "you're not my favourite!!!". The hardest thing was taking their feelings seriously, without laughing at the cuteness.
If it helps, training them to negotiate helps a lot. It lets them get a "win" while doing what you want. It also requires higher level thought, which seems to help suppress emotional tantrums. Finally, it encourages them to make known what is actually important to them.
