(I'm just) minding my own business.
Fig. an answer to a greeting inquiry asking what one is doing. (This answer also can carry the implication "Since I am minding my own business, why aren't you minding your own business?") Tom: Hey, man, what are you doing? Bill: Minding my own business. See you around. Sue: Hi, Mary. What have you been doing? Mary: I'm just minding my own business and trying to keep out of trouble.