Here's what I tell singles every chance I get: Your choice of whom to marry is more crucial than everything else combined that you will ever do to make your marriage succeed. If you choose wisely, your life will be significantly easier and infinitely more fulfilling. But if you make a serious mistake, your marriage may fail, causing you and perhaps your children immeasurable pain.

This principle may sound like a no-brainer, but you would be surprised at the large percentage of singles who have the attitude that says, "I just want to get married, and once I've got my man (or woman), then we'll work things out." Lonely and worried they'll never marry, many singles are so intent on getting to "I do" that they don't invest the necessary time and effort to make a great decision. Most of the failed marriages I have encountered were in trouble the day they began.

But before you swear off marriage completely, be aware that recent research offers great news for singles: A number of studies show that premarital variables can predict which couples will do well and which will not with 80 to 94 percent accuracy. This means you can know in advance if you and your potential mate have a much-better-than-average chance of succeeding in marriage.

Think about it: You don't have to wonder, hope, and believe that you'll have a happy, lasting marriage; you can be very close to knowing it with certainty. And the secret to success begins first and foremost with your choice of whom to marry.

Let me offer what I believe are the four most important factors for choosing a great life partner:

Dr. Neil Warren is a psychologist, popular speaker and the founder of based in Pasadena, Calif. His best-sellingbooks include "Finding the Love of Your Life" and "How to Know if Someone IsWorth Pursuing in Two Dates or Less."

1. Look for someone whose emotional health is solid. Fifteen or twenty years ago, I suddenly recognized something that had eluded me during the early years of my psychology practice. In my frantic attempts to help people keep their marriages together, I had overlooked the most salient truth of all: Most of these people didn't have a "marriage" problem. That is, one or both partners had emotional difficulties, and when those individuals brought their personal problems into the relationship, the marriage went sour.

In 75 to 80 percent of all marriages that eventually end in divorce or separation, at least one of the partners suffers from an emotional health deficiency. Usually, this problem has haunted them for years, long before they got married. I'm so convinced of this that I tell people that no marriage can ever be healthier than the emotional health of the least healthy partner.

The fact is, personality or behavioral problems will not vanish when you get married. If there are qualities about your partner's personality or behavior that you question-such as jealousy, temper, irresponsibility, dishonesty, or stubbornness-ask yourself if you are willing to spend the rest of your life dealing with these problems. Obviously, if the person you are considering has a drug or drinking problem or trouble with sexual integrity, you should make absolutely sure that he or she has worked through the problem well in advance of your marriage.

2. Look for someone who is a lot like you. For couples, similarities are like money in the bank, and differences are like debts they owe. Suppose you received two bank statements in the mail today, one showing the amount of money in your savings account, the other showing the charges on your credit card. If you have a large savings account and little debt, you're in a position of strength and you can weather economic storms. If a financial crisis arises, you have the means to handle it.

But the reverse is also true. With big debts and little savings, you're on shaky financial ground. You have to work a lot harder to cover the bills, and you worry about job security and making ends meet. By now you probably see my point. When two people come from similar backgrounds, they operate from a position of strength. Their relationship is made significantly easier by all the customs and practices they have in common. They know what to expect from each other because they have been raised by parents who were a lot alike. If these two sets of parents were similar economically, racially, religiously, politically, and emotionally, their married children will enjoy a set of "agreements" that form a vital core for their union.

If you want to make a marriage work with someone who is very different from you in background, you will need a large number of similarities in values as permanent equity in your account. That's because every difference you have requires negotiation and adaptation.

One of you has to give a lot, or both of you have to give some. In either case there is a need for plenty of change and energy for negotiations. If couples are unwilling to bend and adjust, they'll experience regular flashes of resentment and frustration. But even if you make the necessary changes, you will still experience the kind of stress that comes whenever significant change is required. If there are too many differences, you may not be able to survive all the strain involved in adapting to each other.