"Morality is a private and costly luxury." Henry Adams

"Morality is doing what is right regardless of what you're told."

Morality is the ability to distinguish between what is right and wrong. However when we talk about morality, we not only allude to that knowledge but the then overpowering urge to adhere to righteousness, which is in actual the import of possessing morality.: To be able to align yourselves with what you consider right.
Henry Adam considers this sense of discretion to be a luxury.. a word we have oft heard in regards of expensive indulgences that provide comfort but are not essential for survival or even for a moderately comfortable life. So when he dubs morality to be a luxury what does he actually mean? Does he mean morality is expensive but then how so because we are not charged money for our decisions or per say?? Or does he mean that morality comes bearing comfort? If we scale morality against the word luxury as we often describe it, then it appears that morality does yield comfort. It does so by relieving us of a guilty conscience by always prompting us towards what is right and fair. Charles Bukowski has been quoted to have said,

"People with no morals, often considered themselves to be more free, but mostly they lacked the ability to feel or love."

Hence from this we can well assume that a moral astuteness in ones conduct leads to peace of mind by ensuring that we do not wrong anybody or anybody's rights from our decisions.

However Henry Adams also considers it to be a private luxury! A private luxury? An interesting choice of words! And here we need to look at what actually ascertain moral decisions as we call them. How do we in our individual capacities decide what is right or wrong and is it same for all. Is what i consider right, right for you and what i consider wrong abominable for you? Not always! We are not all of single mind and thought. Our moral sense is carefully cultivated by our society and religion. We all function in these two spheres taking precedence from these sources or from our own observation deciding that what is right for us.
Thus as Roy Bennet says,

"What one thinks is right is not always the same as what others think is right"

and in this light, morality clearly seems to be a private luxury. If one's moral obligation riots against that of the society, then this peace of mind​ that he has garnered is not the one chartered by society so it does become a private luxury enjoyed by one in his own being.
Henry Adams also declared it be a costly luxury and this cost of morality is what makes it a luxury, a comfort coveted only by few. It takes courage to stand up for what is right, a courage only a few can muster to be able to stand against wrong or unfairness, that might also be at the cost of resisting the societal pressure or going against what may be good for you. One can understand this by imagining themselves in a situation where lying would give leeway from reprimand but then a moral sense would urge that person to stand by the truth in spite of their personal sacrifice as Leon Bulm says

"Morality may consist solely in the courage of making a choice."

Thus it fulfills the last criterion of luxury by ensuring that only the rich can afford to be moral in every conduct of their life not that poor are always immoral but it seems as difficult for poor people to take courage to be morally correct as it seems for them to buy a Mercedes. For the rich begging is wrong and should be abandoned but the poor can't afford this line of thought where "immorality" as the rich deem it becomes their sole way of existence. their condition on life makes it morally correct for them to beg in their perception which again reemphasizes it be a private luxury.

In conclusion, morality is really a luxury, "a private and a costly luxury" and thus the struggle of acting moral at all times is what makes it such a rare approach to life.
I would end it with a quite by Ernest Hemingway

"So far, about morals, i only know that what is moral is what you feel good after, and what is immoral is what you feel bad after"