You want to know on what our faithfulness is founded? I would say, in broad outline, that it is based on loving God, which makes us overcome all kinds of obstacles: selfishness, pride, tiredness, impatience|... A man in love tramples on his own self. He is aware that even when he is loving with all his soul, he isn't ...
When you find yourself worn out or fed up, go and confide in Our Lord, as that good friend of ours did, and say: "Jesus, see what you can do about it. Even before I begin to struggle, I am already tired.'' He will give you his strength. (The Forge, 244)
"The holiness that Our Lord demands of you is to be achieved by carrying out with love of God your work and your daily duties, and these will almost always consist of small realities.”
SAINT JOSEMARÍA, Founder of Opus Dei