Nancy Reagan Proved the Power of Partners in Leadership As President, Ronald Reagan reshaped American government and politics. He always said he could not have done it without his Nancy.

Very rarely do we ever "go it alone."

Yes, this is a nation that celebrates individuality, and the attraction of entrepreneurship is usually built on the idea that a single person can take her talent, her will and her innovation and make it into something better than even the largest corporations could ever offer.

But we're never really alone. Usually, we have a partner, someone next to us each night, even if that person doesn't follow us into the office each day. In the end, this partner is more important than any coworker we have, any team we manage, any vendor or customer. It is our spouse, or significant other.

Which brings us to Nancy Reagan.

Mrs. Reagan, who died Sunday, is being praised for her role as the longtime partner of Ronald Reagan, during his political revolution in the 1970s, his presidency in the 1980s, and his long health decline in the 1990s, until his death in 2004.

It isn't easy to be a First Lady. If you think it is, reflect for a moment on your own personal relationships, your own spouse, and recall all the times that person gave you strength, advice and a willing ear during key decision points.

Then, once you've gotten full appreciation of the role that person played, imagine a world where that spouse was constantly under the microscope of the media, your board of directors, your customers and your competitors. Where every fashion decision your spouse made was exposed, where every decision he or she made public was questioned and every move both of you made was fodder for debate.

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It takes a certain type of person to be this kind of partner, and Nancy Reagan faced more criticism for her influence than most in the 20th Century, whether for her dress purchases, her belief in horoscopes, or the iron-clad protection with which she seemed to cloak her husband. But it always seemed silly to critique the influence of a First Lady – whether it was Reagan in the 80s, Eleanor Roosevelt in the 30s and 40s or Hillary Clinton in the 1990s – simply because they had a dominant point of view. In fact, nowadays, it seems downright sexist, as if these women who stood beside their powerful husbands should not have had an influence at all.

In truth, having a strong and powerful personal partner is actually proven to be a great determinant of your success. Interestingly, the correlation between a strong spouse and success holds up regardless of gender and irrespective of whether the couple was a dual-income family or a single-income family.

In business, Indra K. Nooyi, the CEO of PepsiCo, raised hackles a few years ago when she suggested that as a woman, she was constantly forced to make sacrifices between being a mother and being head of a multinational company. She admitted she had to rely on her husband for raising the family. But she also intimated that her husband's role -- think of it as First Spouse of Pepsi -- was the most punishing.

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"The person who hurts the most through this whole thing is your spouse," Nooyi said. "There's no question about it."

In the end, your life partner is part of your life and part of your ability to lead. Those roles should never be discounted. They can be important no matter what type of spouse or partner you have, whether that person is directly involved in your business, manages a successful business or career separately or simply stays home to raise a family or write the Great American Novel.

Nancy Reagan proved that there are only really two requirements to be, as the Obamas put it in their statement of condolence, the exemplar of how to be a First Lady. You need to be there, always at your partner's side, available for any or all help. And you have to love that person deeply. Love, as Pierre Teilhard de Chardin wrote, is, after all, "a sacred reserve of energy." Love isn't something that might be listed as a requirement for success at Harvard Business School, but those who have experienced it during their own trials of leadership know love is a vital and sustaining force, hard to explain, impossible to reciprocate, and a unique reminder of our blessings in this world, both in business and in life.

Here, in the love department, the Reagans were an enduring example. Put aside all politics, and you see a couple that legitimately loved one another. President Reagan was famous for his hand-written love letters to his wife, captured perhaps best in one just before Christmas:

"Whatever I treasure and enjoy -- this home, our ranch, the sight of the sea -- all would be without meaning if I didn't have you," he wrote. "I live in a permanent Christmas because God gave me you. As I write this, you are hurrying by -- back and forth doing those things only you can do and I get a feeling of warm happiness just watching you. That's why I can't pass you or let you pass me without reaching to touch you. (Except now or you would see what I'm doing.) I'll write no more because I'm going to catch up with you wherever you are and hold you for a moment."

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In just that note, one can see the reliance Ronald Reagan placed on his Nancy, that there could not have been a Reagan Revolution in this country with just one Reagan.

It's a reminder that leadership needs a kind of love and support, which, like the air we breathe, is around us, gives us life but we don't see or even regard most days. Yes, we can be powerful, successful people as individuals. But true fulfillment of our own potential only comes when we share it and cultivate it with someone who knows us -- protects us, supports us, loves us to our very graves -- beyond all others. Here, we can thank Nancy Reagan for being an unmatched example.