In YC's case, the number one cause of early death for startups is cofounder blowups.

If you look at successful pivots, they almost always are a pivot into something that the founder wanted. Not a random made up idea.

You want an idea that turns into a monopoly. But you can't get a monopoly, in a big market right away; too much competition for that.

Good startups usually take 10 years.

Great execution towards a terrible idea will get you nowhere.

You need to have a culture where people have very high quality standards in everything the company does, but still move quickly.

The startups that do well are the ones that are working all the time.