And recently, the flame-haired royal has also been applying that motto to her wardrobe – proving that thrifty and thrilling go together quite nicely.
Although she looked the picture of elegance as she stepped out in purple at Elton John's annual aids fundraiser on Wednesday, she was actually recycling a tried and tested look.
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Her sweeping, floor-length silk trimmed gown had already seen the red carpet treatment when she attended a Children in Crisis charity in 2005.
On Monday, the Duchess also attended a launch party for AllSaints Spitalfields swathed in an affordable and elegant ensemble - all from the High Street outfit.
Her snappy black blazer cost only £250 and was teamed with an even more bank friendly £40 pencil skirt.
No matter what the price tag, the one constant in Sarah's wardrobe is her devotion to her daughters, Princesses Beatrice and Eugenie.
She was recently spotted wearing a gold bracelet emblazoned with Eugenie's name spelled out in gems.
The mother-of-two also stepped out clutching a bag with both girls' faces emblazoned on the front.