I tell people to work on the practical side - like the MBAs in Sustainability - but also on your inner life. You need emotional and spiritual capital because you're effectively standing outside the existing system.

What's it like to give yourself permission to stop when it's not just about making another million, but saving a million lives (or making a world of difference)?

I adore city life, but recognize that living and working together in close quarters presents huge challenges - and that it's not going to get easier as we continue to grow and welcome people from around the world.

This week, I went looking for new ideas about how technology can help drive social change and ways that people like us can, as it were, plug in.

When everything is humming, even when I've been working all night, I feel great, alive, competent. It's the rest of my messy life that's hard.