It's a parent's job to teach their children the lessons of life and try to instil them with good habits for the future.
And Prince Harry once opened up about the household "obsession" he lives by after it was drilled into him by his father King Charles.
It is also a trait shared by older brother Prince William.
But he admitted that at first, it was something that absolutely baffled wife Meghan Markle, who was left confused by it.
And the habit? They are all obsessed with turning off lights in rooms when they are not in use and only using limited lighting when it's dark.
Speaking about their dad in the documentary Prince, Son and Heir: Charles at 70, Harry said: "He's a stickler for turning lights off.
"And that's now something that I'm obsessed with as well, which is insane because actually, my wife goes 'Well, why turn the lights off? You know it's dark'.
"I go 'we only need one light, we don't need like six', and all of a sudden, it becomes a habit and those small habit changes he's making, every single person can do. And I think that's one of the key lessons certainly that I felt that he taught us."
It's no secret that the King has an interest in environmental and green issues - and is also said to be keen not to waste money.
And now it has been reported that he has turned down the thermostat in Buckingham Palace in an energy-saving measure that has reportedly left staff shivering.
The new monarch has dropped the temperature of the Palace swimming pool, with staff who are allowed to use the pool noting it is a lot colder, a source has claimed.
They told The Sunday Times: "A few people using the pool have noticed that the temperature of the water has dropped, and it is quite a bit cooler than it used to be. They have been told the King has had the heating turned down."
The pool was commissioned by King George Vl in 1938 as he wanted to ensure privacy for his daughters Princesses Elizabeth and Margaret who had been having lessons at a nearby Bath Club.
It is claimed the King has been keen to reduce the royal household's energy use which has been a priority of his in recent years.
So far he has already installed solar panels at Clarence House, his London residence, and his country residence Highgrove, in Gloucestershire. At Highgrove, waste water is used in the gardens for the plants and flowers.
