This heavily applies to software development too.

In the inverse, people for some reason with software like to assume the natural state of code is to work. If you assume it doesn't and look for spots where it could fail then, you find the problems.

It's amazing what a state of mind can do.

Many years ago my lecturer used to hammer this point home (he wrote telecoms systems back in the 'old days' (80's/early 90's).

Good guy, bit odd but a hell of a programmer.