The “terrible twos” or “terrible threes” often refer to the emotional turbulence toddlers experience as they grow. This age can be challenging because young children struggle to regulate their emotions, leading to frequent mood swings and meltdowns. However, these fluctuations are normal and not a sign of bad behavior, according to Dr. Paula Levine, a psychiatrist. Understanding this emotional development can help parents cope with their toddler’s moodiness and support them through this phase.
https://www.parents.com/toddlers-preschoolers/discipline/improper-behavior/why-are-toddlers-so-moody