One of the keys to focus, and why I said cofounders that aren't friends really struggle, is that you can't be focused without good communication.

A small communication breakdown is enough for everyone to be working on slightly different things. And then you loose focus.

If someone is choosing between joining McKinsey or your startup it's very unlikely they're going to work out at the startup.

Be suspicious of any work that is not building product or getting customers.

Facebook has this famous poster that says move fast and break things. But at the same time they manage to be obsessed with quality.

More important than starting any startup, is getting to know a lot of potential co-founders.

If you ever take your foot off the gas pedal, things will spiral out of control, snowball downwards.