"Doubt is a pain too lonely to know that faith is his twin brother. Doubt is a foundling unhappy and astray, and though his own mother who gave him birth should find him and enfold him, he would withdraw in caution and in fear."

Next Quote

[D]on't grow old. With age comes caution, which is another name for cowardice.... Whatever else you do in life, don't cultivate a conscience. Without a conscience a man may never be said to grow old. This is an age of very old young men.

— Hesketh Pearson