One important fact about people's virtue and vices is that, once acquired, they are strongly entrenched, precisely because they involve so much more than mere tendencies to act in certain ways. A change in such character traits is a profound change, one that goes, as we say, 'all the way down'. Such a change can happen slowly, but on the rare occasions when it happens suddenly, the change calls for special explanations-religious conversion, an experience that changes the person's whole outlook on life, brain damage, or drugs. It is certainly not a change that one can just decide to bring about oneself overnight, as one might decide to break the habit of a lifetime and cease to have coffee for breakfast.
That the virtues are not merely tendencies to act in certain ways is not an unfamiliar thought. What is more unfamiliar is the Aristotelian idea that they are not only character traits but excellences of character. Each of the virtues involves getting things right, for each involves phronesis, or practical wisdom, which is ability to reason correctly about practical matters. In the case of generosity this involves giving the right amount of the right sort of thing, for the right reasons, to the right people, on the right occasions.
'The right amount' in many cases is 'the amount I can afford' or 'the amount I can give without depriving someone else.' So for instance, I do not count as mean or even ungenerous when, being relatively poor, or fairly well off but with a large and demanding family, I do not give lavish presents to richer friends at Christmas. Nor do I count as mean or even ungenerous if I refuse to let people exploit me; generosity dose not require me to help support someone who is simply bond idle, nor to finance the self-indulgence of a spendthrift. Any virtue may contrast with several vices or failings, and generosity contrast not only with meanness or selfishness but also with being prodigal, too open-handed, a sucker.