It really is true that you become an average of the people you spend the most time with.

You want to continue to be run by great products, not process for it's own sake.

Cofounder relationships are among the most important in the entire company.

You really want to know your cofounders for a while, ideally years.

The most common post YC failure case for the companies we fund, is they're incredibly focussed during YC on their company... and after they start doing a lot of other things. They advise companies, they go to conferences, whatever.

No growth hack, brilliant marketing idea, or sales team can save you long term if you don't have a sufficiently good product.

If someone is difficult to talk to, if someone cannot communicate clearly, it's a real problem in terms of their likelihood to work out.