Error messages that report without helping

Forbidden: "Oops, something went wrong! Your payment wasn't successful as an error occurred" → OK
Instead: "Payment failed. Update your payment details and try again" → Update payment details

What this rule looks like

Forbidden

Instead

An error message has three jobs: say what happened, say why where it helps, and give the way forward. Then:

Never blame the user. Not "you entered an invalid card number" but "that card number doesn't look right".
Cut the apology. "Please", "sorry", "oops", "unfortunately" add length and delay the useful part. A cheerful "Oops!" above a failed payment is worse than nothing.
No system voice. No codes, stack traces or internal terminology in front of a user.
Make the heading and the button descriptive enough to work alone. Someone who reads only "Payment failed" and the button label can recover without the paragraph.

See P-01 for *where* the message goes and F-37 for field-level validation text.