This is one ancient Chinese proverb that has been a life direction for many people.
Metaphorically, if you interpret it literally, it means that you’re heading to a destination riding a horse… if the horse dies on the way, get down onto the ground and start walking !
You don’t have a choice but to walk to reach your destination. Don’t sit under a tree and wait to hitch a ride. Don’t waste time.
Just hope you will catch another horse along the way to cut short travel time.
Even if you only get a cow which is slower, you should seize it first to continue your journey while on the look for a horse that could travel faster.
A wisdom that has been passed on for generations.