What life lesson does Billy learn when he visits the old man to talk about trapping?

Billy goes to visit an old man and asks him about trapping. The old man is bedridden and doesn't seem to offer any real advice about how to catch the wolf. He does say that Billy's quest is like trying to catch a snowflake . You can catch it but when you open your hand, it is simply gone. As he prepares to leave the house, the woman who is apparently the man's caregiver says that the old man would be completely alone if not for her. She then tells him that it could happen to him as well.