The Customer Is Mostly Right
The most important lesson I ever teach younger engineers is this:
Solve the customer's problem, not the one you wish they had.
I call it The Parable of the Bridge Builder.
A wealthy man walks into a bridge builder's office.
"I'd like a suspension bridge," he says. "Six lanes. Railway line on top. Finest steel and concrete money can buy. Money is no object."
The bridge builder is intrigued.
"Where would you like this bridge?"
"In front of my house."
The builder blinks.
"...Why?"
"Well," the man replies, "there's a small dip in my driveway. When it rains, water collects there. Sometimes I step into the puddle and my shoes get wet."
He sighs.
"This cannot continue."
At this point, every engineer in the room has already designed twelve better solutions.
Fill the dip.
Level the driveway.
Build a small footbridge.
Buy the man rain boots.
Teach him to look down occasionally.
Problem solved.
Except...
The customer did not ask for any of those.

