[pearl] of wisdom

a valuable piece of advice or knowledge gained through experience

The idiom "pearl of wisdom" originates from the practice of valuing pearls as precious gems and symbols of wisdom. Pearls are formed within oysters as a result of an irritant, and their rarity and beauty make them highly prized. Similarly, a "pearl of wisdom" is used to refer to a valuable piece of advice or insight gained through experience. The metaphor suggests that, like a precious pearl emerging from an oyster, wisdom can be found within the challenges and irritants of life.

The old man shared a pearl of wisdom with the young couple, advising them to cherish every moment together.
In her commencement speech, the speaker imparted a pearl of wisdom to the graduating students about the importance of resilience in the face of adversity.
As a mentor, he often provided pearls of wisdom to his protégés, guiding them through the complexities of their careers.
Grandma's stories were not only entertaining but also filled with pearls of wisdom that reflected her years of life experience.
The self-help book promised to offer readers numerous pearls of wisdom to navigate the challenges of personal growth and success.