From C. S. Lewis:
“Fine feelings, new insights, greater interest in ‘religion’ mean nothing unless they make our actual behavior better; just as in an illness ‘feeling better’ is not much good if the thermometer shows that your temperature is still going up.” 
Lewis wrote these words in Mere Christianity in 1952. Some parts are dated or were never accurate in the first place (e.g., don’t take marriage advice from a single man writing during the Eisenhower administration). But what is remarkable is not what he gets wrong, but the great deal he gets right.
 C. S. Lewis, Mere Christianity (New York, NY: HarperOne, 2001), 210.