Hmm. It's more like someone comes back from a long wilderness trip or a hike through Europe and they go on and say "I've learned that you don't need 30 kg of luggage". Or someone who's built a good relationship saying "I've learned you can choose not to be jealous or dependent".
I've seen all four combinations of frantic/measured and smart/stupid startups, and I think that measured + smart is the way to go. But I also think that this is one of those lessons you have to learn from experience.
Not easy, but measured. In general I'd rather have someone who maybe thinks about a problem while having a life during the weekend then walks in on Monday with a place to start from, than someone who slept under the desk in between heroic coding sessions. There's a place for both, but having the time and mental energy to gain and maintain perspective is also necessary. You (or at least I, and many people I've worked with) do better work when they have a high thinking to typing ratio.
I've seen all four combinations of frantic/measured and smart/stupid startups, and I think that measured + smart is the way to go. But I also think that this is one of those lessons you have to learn from experience.