Imitation of Christ

Grave est assueta dimittere, et gravius est contra propriam voluntatem ire. Sed si non vincis parva et levia, quando superabis difficiliora? Resiste in principio inclinatini tuæ, et malum defere consuetudinem, ne forte paulatim ad majorem te ducat difficultatem. O si adverteres quantum tibi pacem et aliis lætitiam faceres, temetipsum bene habendo, puto quod sollicitior esses ad spiritualem profectum. 

It is a hard thing to break through a habit, and a yet harder thing to go contrary to our own will. Yet if you don't overcome slight and easy obstacles, how will you overcome greater ones? Withstand your will at the beginning, and unlearn an evil habit, lest it lead you little by little into worse difficulties. Oh, if you knew what peace your holy life would bring to yourself, and what joy to others, I think you would be more zealous for spiritual profit.

Imitation of Christ, I, 11:6