Autism from a mama who has been there. I am going to try to post every day this month. Please feel free to ask questions in the comments.
Comfort: self-harm, stimming, and ritual.
Young children don't know why they feel the way they do. And some times they feel too much. The world is full of stimulation, we automatically block most of it out, but autistic kids have to be taught how to do that in healthy ways.
Before that happens, autistic kids usually come up with their own ways, unhealthy ways.
Self-harm: the child intentionally hurts his/her self. This flood of controlled stimulation temporarily blocks out all other stimuli. Running into walls, head banging, biting, scratching, are common; be aware that these are all forms of self-harm. You may need professional help to treat the damage and to help your child end these behaviors.
Stimming, although not physically harmful, is another unhealthy coping mechanism. The child focuses their complete attention on a repetitive motion blocking out all other stimuli. Hand flapping, turning in circles, nodding, and clapping are disruptive and can block out crucial situational information. Fire, traffic, and other potentially dangerous situations need to be the focus. As overwhelming as situational awareness can be, it is a vital life skill.
Ritual, almost everyone has some form of ritualistic behavior. From a kiss goodbye to saying "bless you" when someone sneezes, most ritual action doesn't interfere with the function of everyday life. You want to pay attention to your autistic child's rituals. Is the routine becoming more complicated? Does not performing the ritual prevent further movement, freezing your child in their tracks? Are there unhealthy ideas associated with doing or not doing the method? The earlier you can catch harmful ritualistic behavior, the easier it is to stop it and redirect.
Autism is a family disability, and you need all eyes on deck. Working together, you can keep that wall from building itself back up because it will try. Break that wall down and keep it down because your child is worth it.
Celebrate the small stuff. Be flexible. Laugh.