Keep your goal before you...

Keep your goal before you and remember that lost time never returns. Only by careful diligence will you acquire virtue. If you begin to grow lukewarm, you will become spiritually ill; but if you see that you grow in ardor, you will find great peace and your labors will grow lighter, all because of God's grace and your love of virtue.

The fervent and diligent man is ready for anything that happens. It takes harder work to eradicate faults and subdue passions than to engage in strenuous physical labor. If you do absolutely nothing about your small faults, you will, little by little, fall into greater ones. If you spend your day profitably, then your evening will be enjoyable. Watch over yourself, admonish yourself, and spur yourself onwards, and no matter what happens to others, never neglect your spiritual welfare. 

The Imitation of Christ, Thomas a Kempis, 42-43