Q. Should you believe what people tell you?
In other words, give other people the benefit of the doubt, and put the most positive construction you can on what they say (and do).
Nonetheless, people do let us down often enough to make us disillusioned. I for one try to believe what I am told, but I examine the evidence closely. There are certainly times when it is obvious that someone is trying to pull the wool over your eyes.
I recall the London Jewish Chronicle saying that they wouldn’t take at face value any communication that was signed “Sh. Lemiel”, though they once got a letter from “M. Le Goy” and subsequently discovered that there was a real person of that name, who was of French-Mauritian descent.
The rule I have adopted is the Biblical verse, Chacham einav b’rosho – “The wise person has eyes in his head” (Kohelet 2:14).
Try to use your eyes and not be too gullible. It doesn’t always work, but it helps.