While scientists have yet to concoct a love potion, their research is providing some helpful tips for a successful marriage. Marry a similar spender Tightwads are likely to tie the knot with individuals who throw caution to the wind when spending money … often to the detriment of the marriage. Scott Rick of the University of Michigan's Ross School of Business and his colleagues analyzed surveys of more than 1,000 married and unmarried adults and found that people tend to choose their spending opposites as romantic partners. The study also showed, however, that the financial opposites had greater conflicts over money and lower marital satisfaction in the long run than those whose spending tendencies were similar. "Even though a spendthrift will have greater debt when married to another spendthrift than when married to a tightwad, the spendthrift is still less likely to argue about money with the other spendthrift," Rick said. Have a lot of sex You've likely met a neurotic in your lifetime, the person who gets upset easily, often has mood changes and worries constantly. Turns out, that personality trait doesn't mix well in relationships and is more strongly tied to negative marital outcomes than any other personality type, according to Michelle Rusk and James McNulty of the University of Tennessee. The pair found that frequent sex could be the answer. Neurotic newlyweds who had lots of sex were just as satisfied with their marriages as their less neurotic counterparts were, according to the study published in the October 2010 issue of the quarterly journal Social Psychological and Personality Science. Even if the sex isn't good now, keep it up: Another study found it may get better with age. Men in their 50s are more satisfied with their sex lives than men in their 30s and 40s, according to a survey published in the February 2006 issue of the journal BJU International. The men in their 50s recorded similar levels of satisfaction as 20- to 29-year-olds. Say "Thank you" and "we" Two words that can go a long way: “Thank you.” In 2007, researchers from Arizona State University asked married partners and student roommates whether they appreciated the chores done by the other person. While most said they felt gratitude, many hadn't relay these feelings to their partners, assuming "he or she just knows." Results also showed individuals who felt appreciated by their partners had less resentment over any imbalance in labor and more satisfaction with their relationships than other study participants did. Another simple word that can boost partner pleasure: “we.” A study published in the September 2009 issue of the journal Psychology and Aging found that spouses who used couple-focused words such as "we," "our" and "us" when talking about a conflict also showed more affection, fewer negative behaviors such as anger, and lower physiological stress levels during the disagreement. Using words that expressed separateness, such as "I," "you," and "me," during the discussion was associated with marital dissatisfaction. Be tough Speaking of spouses driving one another mad, not to worry, says one researcher who has found that some marriages actually thrive on negative behaviors. For some couples with serious problems, the best way to breed a happier marriage seems is by placing blame on each other, telling the other person to change, and being less forgiving, according to a decade of research on the topic by University of Tennessee psychologist James McNulty. Essentially, he said, happy couples behave in certain ways that, rather than making them happy, may simply reflect their glee. In fact, McNulty has found that if unhappy couples practice these same positive thoughts and behaviors, their relationships seem to get worse over time. He added that there's evidence to suggest placing blame and other negative exchanges can motivate partners to change. His research suggests marriage counselors might do well to encourage troubled couples to be more critical of one another. Work hard at it Romantic love can stand the test of time if you apply elbow grease. In a study published in 2009 in the journal Review of General Psychology, researchers analyzed surveys of more than 6,000 people, including new relationships and marriages that had lasted at least 20 years. A surprisingly high number of people were still very much in love with their long-term partners, though the researchers drew a distinction between romantic love, which can endure, and passionate or obsessive love, which often fades after the beginning of a relationship. The key to keeping that romance alive: hard work. Research has suggested these couples spend time and really care about the relationship; they seem to be able to resolve conflicts relatively smoothly, said Bianca Acevedo, a postdoctoral researcher at the University of California, Santa Barbara, who authored the study while she was a graduate student at Stony Brook University. Studies have also shown novel experiences can stimulate the production of the neurochemicals dopamine and norepinephrine, which show up in the brain in the early, blissful stages of a relationship.