If someone is circling the drain, they are very near death and have little time to live. The phrase can also describe a project or plan or campaign that that is on the brink of failure.
The idiomatic expression 'drive home' means 'reinforce' as in 'The company offered unlimited technical support as a way to drive home the message that customer satisfaction was its highest priority.'
This means that it is better for people to mind their own business and to respect the privacy of others. ('Good fences make good neighbors' is the American English spelling.)