Find that thing you are super passionate about. A lot of founding principles of Facebook are that if people have access to more information and are more connected, it will make the world better; people will have more understanding, more empathy. That’s the guiding principle for me. On hard days, I really just step back, and that’s the thing that keeps me going.

It took 10 years to go from building the initial Smartphone to reaching the mass market. BlackBerry came out in 2003 and it didn't get to about a billion units until 2013. So I can't imagine it would be much faster for VR.

Just because you can build a machine that is better than a person at something doesn't mean that it is going to have the ability to learn new domains or connect different types of information or context to do superhuman things. This is critically important to appreciate.

The trick isn't adding stuff, it's taking away.

In a recent survive of Millennials around the world asking what most defines our identity, the most popular wasn't nationality, ethnicity or religion. It was "citizen of the world." That's a big deal. Every generation expands the circle of people we consider one of us. And in our generation, that now includes the whole world. This is the struggle of our time. The forces of freedom, openness, and global community against the forces of authoritarianism, isolationism, and nationalism - forces for the flow of knowledge, trade, and immigration, against those who would slow them down.

For the first time we're allowing developers who don't work at Facebook to develop applications just as if they were. That's a big deal because it means that all developers have a new way of doing business if they choose to take advantage of it. There are whole companies that are forming whose only product is a Facebook Platform application.

I hope that Facebook and other Internet technologies were able to help people, just like we hope that we help them communicate and organize and do whatever they want to every single day, but I don't pretend that if Facebook didn't exist, that this wouldn't even be possible. Of course, it would have.