Silver lining

According to the Cambridge Dictionary "silver lining" (noun) means an advantage that comes from a difficult or unpleasant situation. Example:

- When things look black, there's always a silver lining.
- The injury had a silver lining: it enabled Blake to spend his father's last weeks with him. 

Other definitions:

1. Use the term silver lining when you want to emphasize the hopeful side of a situation that might seem gloomy on the surface.

2. If you talk about a silver lining, you are talking about something positive that comes out of a sad or unpleasant situation.
- The fall in inflation is the silver lining of the prolonged recession.

The common expression "every cloud has a silver lining" means that even the worst events or situations have some positive aspect. You are most likely to remind a sad or discouraged friend that there is a silver lining as a way of cheering him up. The origin of the phrase seems to be John Milton's 1634 poem "Comus," which includes the line, "Was I deceived? or did a sable cloud/Turn forth her silver lining on the night?"

Fonte: Vocabulary.com; Collins Dictionary; Cambridge Dictionary.