What is the most useful thing a stranger has ever told you?

[HeartbreakKid92]

Not looking for inspirational quotes. Looking for specific useful information or practical advice from someone you did not know that actually changed how you do something or think about something. Could be from a conversation on a train, someone at a party, a comment online, a shop assistant. The smaller and more specific the better.

[Phil80]

A plumber I had never met looked at my boiler and said: the one maintenance job that actually extends the life of a boiler is bleeding the radiators and adding inhibitor once a year. Takes thirty minutes. Has been true every year since

[SouthernBuffer]

A taxi driver told me that the best time to negotiate anything is when the other person has just said yes to something else. Their resistance is lower for about 90 seconds after an agreement. Absurdly useful in retrospect

[WearyCoder]

A stranger in a library told me that if you are stuck on a problem you should write it as a question rather than a statement and your brain processes it differently. Changed how I approach every difficult task

[CMPunk88]

An older woman at a bus stop told me that the secret to not being tired in the afternoon is to eat lunch before you are hungry rather than after. I thought it was nonsense. It is completely true and I do not know why it works

[WWEHarry78]

Someone at a wedding said: the way to tell if someone is genuinely listening is whether they reference something you said earlier in the same conversation. That is the whole test. Completely changed how I pay attention

[Sinead_47]

A pharmacist told me that the expiry date on sunscreen is for the UV protection not the cream itself. Throwing it out because it has expired and not replacing it is worse than using last year's slightly less effective bottle. Used that information every summer since

[DarkSideRichard47]

Duck. wait no it was "aye up me duck"