As I have said before, the code of Chivalry serves as a self-imposed moral check on the behavior of the powerful toward those less powerful than them. It is for this reason that Compassion is key among those virtues, for without thinking of the needs and feelings of others there is no motivation for right action.
Just as Prowess may be practiced until skills become second nature, so can Compassion. To become a better fighter, one must test oneself against difficult opponents, and for Compassion it is no different. It is easy to consider the feelings of those you are close to, but harder for those you do not know, or that you do know and do not like. Likewise it is more challenging when the acts required by Compassion demand sacrifices, be they of time, effort, resources, or pride.
Like any other virtue, perfection is unattainable, but by striving to achieve it we are all made better people.