I love the way young devs code assuming the product owner won't change their mind

That's called "experience"... or lack thereof!

We learn more from pain than pleasure 😉

This phrase to my mind everytime it happens - ''Oh you sweet summer child''

I usually make EVERYTHING a variable, the hard code some things for production, and I breakdown the software into so many functions, each function doing one thing and one thing only...that way when things change, I can easily just write up another function and hook it up, and take the others out of the main program flow