"It's not the size of the dog in the fight that matters, it's the size of the fight in the dog"
in other words?
It's not how big you are that matter, it's how good you are.
Could be applied to people, businesses, etc.
It's a famous quote by Mark Twain. When two dogs get into a fight, it's not the biggest dog that wins. Rather it is the dog with more fight or determination that ends up winning. The quote means with good attitude and effort you can overcome a lot of obstacles.