There are two nice proverbs about work and horses which I often share with my colleagues to describe few ideas in clear and easy way.
The first one is from Russia:
Horse worked harder than other on the farm, but don’t became a farm owner
I think it’s a good example, if you need to describe that you don’t need work harder, but more effective and smart.
Another is from the East:
Get off the horse if she died
It means that it doesn’t make sense to work on obsolete idea or goal. You need to select another one.
Sometime you need to be brave enough to realize that work you’re doing does not makes sense anymore. It looks stupid to continue with it.