On completion of Long Day's Journey Into Night, O'Neill is said to have given it to his wife, insisting that it shouldn't be published until 25 years had elapsed.
Remember, this play is set in 1912. While I am hopeful that more than 100 years later we have more effective treatments to deal with the problems faced by the Tyrone (O'Neill) family, I still can't imagine that any one of them would be easy to deal with.
The tragedy is in the suffering. Elder brother James drank himself to death at the age of 45, dying within three years of his parents.
Eugene O'Neill himself suffered significant health issues which must have influenced his writing and I wonder what his plays would be like had he not known such ill health and family distress.
Would he still have received the Nobel Prize for Literature (1936)? Would he have won the Pulitzer Prize for Drama (1957)? Perhaps, but we'll never know.