This idiom means that everyone will experience a time of success or good fortune, even those who are currently struggling or seem unlucky. It suggests that things eventually even out for everyone.
Here are some examples of how it can be used:
* "Don't worry about being passed over for that promotion. Every dog has its day, and you'll get your chance eventually."
* "He's been through a lot of tough times lately, but I know every dog has its day and he'll find his way back to happiness."
Let me know if you have any other idioms you'd like explained! 😊