This quotation, made by the lawyer Alfieri at the end of the play, means that in order to live in a community with other people, we have to meet them halfway, not behaving like Eddie Carbone and putting ourselves before the community.

Alfieri recognizes the importance of compromise for a fully functioning society to work. Otherwise, if we simply do as we please, if we act from purely selfish motives as Eddie Carbone did, then we will undermine the stability of the communities in which we live.

That's what Eddie did when he informed on Marco and Rodolpho to the authorities for being undocumented immigrants. Even though they were his wife's cousins, he had no compunction in informing on them, so full of jealousy was he over his niece Catherine's burgeoning relationship with Rodolpho.

Instead of settling for half, as most people do, Eddie wanted it all. And the consequences of his selfishness were catastrophic indeed. Alfieri will mourn Eddie's tragic death, but what he won't do, what he can't do, in fact, is condone the way Eddie lived his life.