Money and sex are the two things responsible for driving a toxic wedge in most relationships. Here is something I could never understand. How does a woman, who has been conditioned her entire life to believe that the man is the main breadwinner in the family, shift gears and take on a new role? A role that requires her to bring home most of the bacon.

Like any great social change, “The Miranda Complex” is not without its victims. Remember Miranda in Sex and the City? She was the lawyer dating the bartender, whose income and social skills were no match for hers. Today, many women are discovering firsthand that a relationship between a successful woman and a man with less income is very complicated. It brings up a lot of different issues that, over time, could end up hurting both partners and breaking up relationships.

Today, two-thirds of women over 40 earn more than their men, so it’s not hard to understand why so much trouble is brewing in paradise.

“The woman who makes more money than the man creates a problem,” says psychiatrist and relationship expert Dr. Gail Saltz. Just as women have been conditioned to be cared for, men see themselves as providers. When that role is taken from them, their masculine psyche is badly bruised.

“Our respect for our partner is based on whether they are living up to their gender expectations,” says Professor Janet Reibstein, psychologist and author of The Best Kept Secret: Men & Women’s Stories of Lasting Love. “Higher-earning women struggle to respect their low-paid men because social prejudice says a man should keep his wife.

“Women want to be in charge of their lives and careers, but they also have a contradictory need to know that their man will take care of them if need be. When that doesn’t happen, a woman’s sense of femininity and a man’s sense of masculinity is often threatened.

Whether they admit it or not, women will be upset when their man spends his hard-earned money on “man’s toys” that they couldn’t afford without his financial help. Do the most successful men secretly resent it when their wives are spending their hard-earned money? I don’t know. Maybe they will, but don’t say anything because it’s always been their job to be the provider.

When low-income men feel slighted and high-income women feel resentful, there is another part of the relationship that goes downhill very quickly. Your sex life. It’s quite common for women with high incomes to abstain from sex when they don’t get what they think is their due. It doesn’t take long for her to figure out the “one with the golden rules” way of doing business.

A 2006 University of Virginia study of 5,000 women found they were happier when their husbands contributed 68 percent or more of their household income. “Married women have happier marriages when their husband is a good provider,” says Professor Steven Nock, co-author of the study.

Until both sexes learn to disconnect the wiring that defines gender roles, it will be difficult to find the balance that gives both people what they are really looking for.