The highest strength is ...

The highest strength is acquired not in overcoming the world, but in overcoming one's self. Learn to be cruel to thyself, to withstand thy appetites, to bear thy sufferings, and thou shalt become free and able.
 John Lancaster Spalding

Quotes from the same author

Women are aristocrats, and it is always the mother who makes us feel that we belong to the better sort.
 John Lancaster Spalding
Those who believe in our ability do more than stimulate us. They create for us an atmosphere in which it becomes easier to succeed.
 John Lancaster Spalding
The able have no desire to appear to be so, and this is part of their ability.
 John Lancaster Spalding
A principal aim of education is to give students a taste for literature, for the books of life and power, and to accomplish this, it is necessary that their minds be held aloof from the babblement and discussions of the hour, that they may accustom themselves to take interest in the words and deeds of the greatest men, and so make themselves able and worthy to shape a larger and nobler future; but if their hours of leisure are spent over journals and reviews, they will, in later years, become the helpless victims of the newspaper habit.
 John Lancaster Spalding
A Wise man knows that much of what he says and does is commonplace and trivial. His thoughts are not all solemn and sacred in his own eyes. He is able to laugh at himself and is not offended when others make him a subject whereon to exercise their wit.
 John Lancaster Spalding