The most important two high-level takeaways

• Eliminate ego. And you have to be comfortable not being rewarded in the short term.
• Invalidate all the lore. In any given product there are always people who strut around the office like, “You know, I have this gut feeling. It's all about gut feeling". Gut feel is not useful because most people can't predict correctly.

If you can't be extremely clinical and extremely unemotionally detached from the thing that you're building you will make these massive mistakes and things won't grow because you don't understand what's happened.