The man must not be selfish; nor, if the woman is wise, will she let the man grow selfish, and this not only for her own sake but for his.
 Theodore Roosevelt, Theodore Roosevelt; an Autobiography (1913). copy citation

Context

“but, after all, his actions are no worse in the long run than those of the woman who is content to be a parasite on others, who is cold, selfish, caring for nothing but frivolous pleasure and ignoble ease. The law of worthy effort, the law of service for a worthy end, without regard to whether it brings pleasure or pain, is the only right law of life, whether for man or for woman. The man must not be selfish; nor, if the woman is wise, will she let the man grow selfish, and this not only for her own sake but for his. One of the prime needs is to remember that almost every duty is composed of two seemingly conflicting elements, and that over-insistence on one, to the exclusion of the other, may defeat its own end.” source