I stayed up too late and I’m tired and irritable today. Then I caught myself thinking — imagine being small, exhausted, and not having the words or regulation skills yet. Sometimes behaviour is just a nervous system running on empty. When adults are tired we lose patience faster, everything feels louder, and small things take more effort than they should. Most of us still have years of practice masking that — children don’t. Their nervous systems are still learning how to cope, so tiredness comes out as tears, defiance, silliness, or shutting down rather than “I need rest”. It’s a useful reframe for parents because it shifts the question from “what’s wrong with this behaviour?” to “what’s the child carrying right now?” Sleep debt, sensory load, transitions, growth spurts — all of it lowers capacity.