I am trying to weakly correlate this concept to startups. You have to start out dreamy-eyed enough to start. You can deal with reality later.
When Scott Mace and I started CalendarHub and applied to YCombinator in the same year as Justin Khans Kiko, we weren't shooting for lifestyle business. We were shooting for Get-Bought-By-Google or bust. Reality set in later. That was my start, at least I started :).