Humans thrive on habits; it's ingrained in our DNA. It's to our evolutionary advantage not to change. Habits allow us to use less of our thinking power, they keep us safe and they preserve physical energy. We're all resistant to change on some level, so it shouldn't be surprising that children oftentimes have difficulties making transitions.

While triggers that result in meltdowns can be grossly exacerbated in kids with ADHD, sensory issues, developmental delays or those on the autism spectrum, most kids find transitions difficult. Asking a child who's engrossed in an activity to stop then and there to move on to another activity - oftentimes a less desirable one such as cleaning up or having a bath - can be akin to petting the belly of a cat. At minimum, you'll be met with some resistance; at their worst, children who aren't prepared for transitions will lash out physically.