Proverb “Feeding a cow with roses does not give
extra appreciation” means that you shouldn’t waste your effort and time on
people who can’t grasp the meaning and effort of your action to appreciate it
enough. In short, we could say that it means that you shouldn’t waste your time
on someone who doesn’t deserve it. Similar proverb can be “Casting pearl before
swine” which originated in Bible (Matthew 7:6, Jesus’s Sermon on the Mount).
