What a wonderful phrase... I wouldn't go so far as to say that it summarizes the Buddha's teaching but it certainly is high on my list of virtues that should exist in a person. Thinking about it more, it has many meanings:
Mind your own business - why am I busy with the faults of others?
Mind your own business - why aren't I busy fulfilling my duties to study and practice?
Mind your own business - why am I so busy?