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.

... for the top twenty most valuable YC companies, all of them have at least two founders.

You can basically change everything in a startup but the market.

Remember that the idea will expand, and become more ambitious as you go.

You need unstoppable people. You want people that are just going to get it done.

We hear again and again from founders, that they wish they had waited to start a startup until they came up with an idea they really loved.

Unpopular but right is what you're going for.