Plutarch’s morals 

The philosophers tell us that some bodies are composed of distinct parts,as a fleet or army; others of connected parts, as a house or ship; others united and growing together, as every other animal is. the marriage of lovers is like this last class, that of those who marry for dowry or children is like the second class, and that of those who only sleep together is like the first class, who may be said to live in the same house, but in no other sense to live together. but just as doctors tell us that liquids are the only things that thoroughly mix, so in married people there must be a complete union of bodies, wealth, friends and relations. And thus the Roman legislator forbade married people to exchange presents with another, not that they should not go shares with one another,  but that they should consider everything as common property. 

I think that is sound advice.