Everyone who has loved has fought, and Terence doesn’t think this is a bad thing.

"Amantium irae amoris integratio est."

"The quarrels of lovers are the renewal of love."

Amantium ("of lovers") is the genitive plural of amans ("lover"). 

Irae ("quarrels" or "anger") is the nominative plural of ira, irae ("anger, wrath”).

Integratio ("renewal" or "restoration") is a nominative singular noun acting as a predicate nominative. 

Amoris ("of love") is the genitive singular of amor, amoris ("love").

Est - is.