What is your plan
When a kid's behaviour does not make any sense, and I start to feel frustrated I lean heavily on this question:
"What is your plan?"
Often there is a plan. Almost always a coherent plan. Sometimes with some flaws in either logic or execution.
Discussing the plan is how I calm down and how they get to learn something.
As has been remarked to me by a little one: I am also a child with parents. I would also benefit from people asking me that question sometimes.