Even if they’re in a close, committed relationship, every adult needs what used to be known as mad money, said St. Paul financial counselor Ruth Hayden.

“Both people need access to money that they can spend without justifying or explaining it. There’s an agreement that there’s yours, mine and ours,” she said. “This frees up two independent people to be themselves.”

But Hayden stressed that there must be boundaries for what she calls “autonomy money.”

“You have to agree that this spending can’t go against the values embedded in the relationship,” she said. “I’m not talking about an expensive haircut; I mean crossing a line with a moral issue like using that money for drugs or gambling.”

Having some money of one’s own makes it easier for many couples to be honest about their finances. And that, in turn, helps them stay together.

“Many studies find that keeping significant financial secrets is more destructive to a relationship than sexual infidelity,” she said.