I don't say "fie" to my parents, and I don't envsiage saying "fie" to them at any point.
If I were a giant I might say "fie", but not necessarily to them. I would say it in general. Fie Fi Fo Fum, I smell the blood of an Englishman.
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The time will never be ‘just right’.
Start where you stand, work with whatever tools you may have at your command,
and better tools will be found as you go along.