about (one's) business
Focusing on one's own tasks or routine. The phrase emphasizes that one is minding one's own business without any unusual deviation, especially without bothering others. Typically used with the verb "go." I was just going about my business when I was stopped for questioning. Be about your business, everyone, there's nothing to see here.
*about one's business
busy doing something. (*Typically: be ~; get ~; go ~.) Why are you still in the house? It's time to be about your business. Why are you just standing there? You'd better get busy doing something!