This phrase is used to indicate that if people are warned about a potential danger or problem in advance, they're unlikely to suffer consequences. It's similar to the English saying 'forewarned is forearmed'.
Examples
- Spanish: Tienes que estar preparado para el examen final, recuerda que 'en guerra avisada no muere gente'.
- English: You have to be prepared for the final exam, remember that 'forewarned is forearmed'.