Autistic children live in an inner world that is confusing and chaotic, where they have difficulty making sense of everyday life. Routine establishes order in their lives by giving them a safe and secure environment. Routine lets them know what to expect and when to expect it.
Autistic children insist on sameness and an inflexible adherence to routines. Even the slightest deviation from the particulars of an established routine creates enormous anxiety. Adherence to routine becomes obsessively important and any sort of change is a major cause for alarm.
Autism is perpetual and unrelenting hyperfocus, the state of intense single-minded concentration fixated on one thing at a time to the exclusion of everything else. The autistic brain compulsively gives its full attention to whatever the child is doing in any given moment and is oblivious to everything else. Whenever you interrupt routine, you obliterate everything that was in that child’s consciousness and replace it with extreme anxiety.