A blessing in disguise
Definition 1 of 1
Pro Tip 1/3Hidden Positives
Look for the unexpected benefits in negative situations when using this phrase. 
Although the storm ruined our sports day, it was a blessing in disguise as we had a great time indoors.
Pro Tip 2/3Irony Alert
Use this phrase to express irony when an unfortunate event leads to a good outcome. 
I missed the bus and walked to school, but it was a blessing in disguise because I found $20 on my way.
Pro Tip 3/3Optimistic Tone
Use it to show optimism in hindsight, reflecting on past events that had a positive turnaround. 
The vacation I missed due to illness turned out to be a blessing in disguise; I avoided a bad storm.