From Liberpédia

Sacrifice does not mean the rejection of the evil for the sake of the good, but of the good for the sake of the evil. Sacrifice is the surrender of that which you value in favor of that which you don't.

Ayn Rand, Atlas Shrugged, 941

A sacrifice is the surrender of a value. Full sacrifice is full surrender of all values. If you wish to achieve full virtue, you must seek no gratitude in return for your sacrifice, no praise, no love, no admiration, no self-esteem, not even the pride of being virtuous; the faintest trace of any gain dilutes your virtue. If you pursue a course of action that does not taint your life by any joy, that brings you no value in matter, no value in spirit, no gain, no profit, no reward - if you achieve this state of total zero, you have achieved the ideal of moral perfection. You are told that moral perfection is impossible to man - and by this standard, it is. You cannot achieve it so long as you live, but the value of your life and of your person is gauged by how closely you succed in approaching that ideal zero which is death.

Ayn Rand, Atlas Shrugged, 941

The meaning of this regard for the general social interest has frequently been misunderstood. Its moral value was believed to consist in the fact of the sacrifice itself, in the renunciation of an immediate gratification. One refused to see that what is morally valuable is not the sacrifice, but the end served by the sacrifice, and one insisted on ascribing moral value to sacrifice, to renunciation, in and for itself alone. But sacrificing is moral only when it serves a moral end. There is a world of difference between a man who risks his life and property for a good cause and the man who sacrifices them without benefiting society in any way.
Ludwig von Mises, Liberalism, p. 34 [1] (