This week's guest is Martin Griffiths, the Secretary General's Special Envoy for Yemen, a country that's been devastated by civil war. Martin's job is to try to keep open routes to negotiation between the warring parties. He says a mediator has to bring hope to seemingly hopeless situations. Martin speaks candidly about his struggles with depression, the mental toll humanitarian work can have, and the importance of empathy when mediating between sides in a conflict.

"I'm not from Yemen. It's our conflict because it has such dramatic consequences, not only for the people of Yemen more broadly. But the job of a mediator, I think, is to infuse hope into people, to say there can be a solution to this, to come up with ideas as to how they might resolve their inevitable differences. And to give some kind of sense of vision to the people of Yemen, that this doesn't need to go on indefinitely, because in a war, it seems endless to those living through it. While their children don't go to school, they are displaced and disrupted. There seems no possible end. And I think what we do in the United Nations, and in the job that I have, is to try to give people a sense, there is another way, there's a way out of this, and that their leaders need to take it."