ignatius on the long obedience
There flashed upon his mind the idea of the difficulty that attended the kind of life he had begun, and he felt as if he heard some one whispering to him, "How can you keep up for seventy years of your life these practices which you have begun?"
Knowing that this thought was a temptation of the evil one, he expelled it by this answer: "Can you, wretched one, promise me one hour of life?"
I've has a similar thought many times. My desire to follow hard after Jesus. Can I 'keep it up?' for 50 years?