The lesson is that design details do matter, and when you pay attention to them it has a cumulative effect that results in a much better product. You do have to develop a certain amount of callousness to pursue your vision. You don't have to scream and berate people, but when you're sending a design back for the tenth time, you're bound to start thinking "Gosh, this designer is going to think I'm an asshole." A lot of people will just accept something that's not exactly what they want just to avoid potential bad feelings from someone else.
The emotional aspect made it easy and natural for Steve to pursue the design until it was exactly what he wanted. Indeed, it probably made it nearly impossible for him to do anything else. The rest of us have to consciously override social impulses that value getting along and being liked higher than small details. The upside is that we get to manage our response so we can motivate with something other than fear.
