A useful opinion knows what experience it came from.

An opinion becomes more useful when its origin comes with it. Whether a view grew from years of doing something, from one bad experience, or from a story half remembered changes how much weight it deserves, and saying so is a kindness to whoever is listening. Confidence offered without a source is impossible to weigh. Knowing where your own view came from also tells you how firmly to hold it.

Add the source when you offer a view: I did this for a decade, or this happened to me once. Ask the same question of the advice you receive.