Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
We can see from the dedicatory letter to his wife (see "What's Up with the Epigraph?") that O'Neill strives, in this play, to find "forgiveness for all the four haunted Tyrones." Any one of these four deeply flawed individuals can be extremely frustrating. By the end of the Long Day's Journey, though, we find it hard to stay mad at any of them. Life has dealt the Tyrones a tough hand. With each character, O'Neill shows the reason for the ugly, and doing so allows us to understand and feel compassion for them.