Coming to appreciate that the real requirement for healthy growth is not so much the work to be done with the other person but they work we must do on ourselves. When exposed to the old "Childhood Needs" activated by our partner's "Childhood Self" a person must exert significant effort to avoid regressing into his own Child part. Collusion keeps the conflict alive. Staying in the here and now as an "Adult" takes work.
The price of Adulthood is eternal vigilance; you must always know where
your "Child part" is.
But the payoff is as invaluable as the rewards of being an adult.