'Before their letter arrived I had been feeling in low spirits for no particular reason and I was immensely cheered as I read it and saw what the others are doing.' And another: 'Your letters and the news of my brothers help me like a happy dream in the midst of the reality around us!'... And another: 'It's so wonderful to receive those letters and to realize that I'm a friend of such friends!' And another, and a thousand others: 'I had a letter from "X" and was ashamed to think of my lack of spirit compared with his.'
Now don't you agree that the 'letter-apostolate' is effective?