The finished piece should survive the ordinary conditions its maker can imagine.

Making something for ideal conditions is a way of handing the difficulty to whoever uses it. Real life includes dishwashers, dropped handles, cold mornings, children, and hands that are not paying attention, and a maker can picture all of that without much effort. Anything that only works when treated perfectly has quietly transferred its fragility to the owner. Durability is part of the design rather than a bonus on top of it.

Before you call something finished, list the three ordinary things most likely to happen to it. Then check whether it survives all three, and change what does not.