Think it through, and you will sleep well
Joshua Porter explains why UX designers sleep well at night:
People who ruthlessly prototype are in a big way setting their mind at ease because they’ve seen the future… they know what works and what doesn’t. That’s a pretty big deal… people work better when they are calm and fully understand the situation they’re in.
Seems like the “good design is thorough down to the last detail” principle works in favour of both users and designers.