Wine, vodka, gin, a little rum and whiskey, and occasionally, with care, tequila! Also, separate bathrooms, and if necessary, separate houses (my uncle and his girlfriend have kept a river - literally - between them for 25 years!)
On a more serious note, check out Harville Hendrix's "Getting the Love You Want" - it is a very down-to-Earth (no Mars / Venus stuff) about relationships and makes more sense than anything else I've ever read on the subject. In the beginning he establishes a LOT of credibility by listing things people in love say to each other, and as I read the list, I thought, "I said that . . . and that . . . and I was told that . . . and that . . ." - and then he goes on to explain why these are common expressions and feelings.
And then, there's the modern marraige, a la Rod Stewart - a guy finds a woman he just can't get along with, buys her a house, and then never talks to her again . . . ba-bump, ching!