Everyone in Long Day's Journey into Night has some major anxiety about the lost Good Old Days and about old mistakes that still show scars. Both parents express real regret over choices they made in their youth: James wishes he could have been a more diverse actor and Mary seems to wish she had never married James. She is also absolutely haunted by the death of one of her children, and clearly feels guilt over it.
O'Neill switched his name with that of his deceased brother Edmund partly to ensure that the play isn't taken as literal autobiography, but also as a way of giving his brother a life on paper that he never had in real life.
The continual literary allusions provide another way for the Tyrones to avoid confronting current reality.