"And as ye would that men should do unto you, do ye also to them likewise." This so-called "Golden Rule" is unique to the Christian Faith. It is true that similar precepts can be found in other religions, but nowhere in this precise form.
For one thing, the context here is love for one's enemies. Now the Golden Rule is perhaps not so hard to follow (up to a point) in regards to one's friends and loved ones--so long as it does not become too inconvenient. Even so, our motives in following the commandment are usually mixed: either we expect the same treatment in return ("I'll rub your back if you rub mine") or else it becomes an occasion of pride and feeling good about ourselves.
However, it goes completely against the grain of our fallen human nature to behave in a loving, kind and compassionate way toward those who hate and abuse us, even if our behavior does not reflect our true feelings. After all, no one wants to be a door mat, and besides, "What's in it for us?"
The fact is, if we desire to succeed and to "get ahead" in this world, the Golden Rule can become a real obstacle. In any case, is any normal person real capable of truly loving one's enemies?
True enough if our Faith is a hoax and we are merely a higher form of animal struggling to get along in this world the best we can until death overtakes us and we cease to exist. But if we truly are beings created in God's image "a little lower than the angels" and destined for eternal life in the glory of God's heavenly Kingdom, it changes everything.
It is indeed this capacity to love even one's enemies that lifts us above the lower creatures and confers dignity and purpose to a life that would otherwise be meaningless and therefore not really worth living. Nor would God ever command us to do anything that we are inherently incapable of doing. Humanly speaking, it really is impossible to fulfill the Golden Rule, but truly all things are possible through the grace of God.
As God told St. Paul when the Apostle asked three times to remove his "thorn," "My grace is sufficient for thee: my power is made perfect in weakness." This grace, however, is not something somehow added on to our fallen human nature. To be fully human means to be united with God and to be filled with His grace, which is the uncreated energy of God Himself.
"Be merciful, even as your heavenly Father is merciful:" this is the true reason for fulfilling the commandment, because we are all in the truest sense the children of God, and God is love. This, then, is the path we must all strive to follow if we desire that peace, joy and fulfillment only God can give--both in this world and the next.