The best advice I've ever had is this; "Never wrestle with a pig. You both get dirty and the pig likes it!" It came from a participant on "Dr Phil." They were talking about how difficult people can drag you through the dirt and enjoy every minute of it, whilst you end up battered and filthy. It's good advice and it's funny – and it's funny because it's true.
The hardest part of it though is to recognise a pig who wants to wrestle. Time after time, the piggy looks cute and just seems to want to be friends, but one day, suddenly, the piggy hurls itself towards you and it's fight or flight.
Why do we let ourselves get caught up in another's hurt or difficult behaviour? Damaged people can (and do) lash out at others. We all know people who bully because they have been bullied. I'm willing to bet everyone has, at some time, been on the receiving end of someone else's misdirected temper.
But we can't control another's behaviour, we can only control our own.
In short, the "never wrestle with a pig…" advice is really good, but difficult to live out.