[tdr]

Also really good advice:

A year into my first startup, my first major product epiphany was to never, never, ever try to build a product you couldn’t be a user for

You have to have the vision, understand everything around it. Relying only on (potential) outsiders doesn't cut it. You need prioritization, focus (" means saying NO"), simplify the UX... You need to be committed. Otherwise you just get "feature creep"