Over the last few months all my spare time has been spent writing about how to survive anywhere; from the Arctic to offices, and yesterday I was thinking about desert islands. They are the go-to metaphor for survival, and you don't have to look far to see them in popular culture's idea of what survival is all about. But I'm writing about real life, not reality TV, and the real difficulties of desert islands aren't the obvious ones. The island in the picture was the scene of several people's real-life survival ordeals, over a few decades. It holds many challenges physically – there's no easy water source for a start – but the biggest challenges to any castaway are psychological. That's where I'm focusing my attention this week.