If you're married or thinking about getting married, at some point or another you've wondered what better sex in marriage would be like or how sex in marriage could be improved.

Keeping the sexual spark alive in a marriage or in a long-term relationship is easier said than done. However, couples who take time to cultivate and maintain healthy and satisfying sexual relations tend to be more connected with each other and do not suffer from depression, heart problems and other health maladies, experts say.

The daily routines of life — whether careers, children or financial responsibilities — challenge couples to keep alive that flame that initially brought them together. From a practical standpoint, there's less time for sex and intimacy as relationships develop and individual partners take on more responsibilities.

Furthermore, aging brings on a host of physical conditions that can affect life in the bedroom. These include sexual dysfunction, cardiovascular conditions, arthritis and rheumatism, and a host of other problems.

Whatever the reasons for brewing trouble in the bedroom — whether emotional or physical in nature — the good news is that many such problems are easily treated. Moreover, troubles in a couple's sexual relationship are often signs of other problems, and can serve as a warning sign for still bigger troubles ahead.

"A good sex life is an important part of an individual's overall health," says Mark Schoen, Ph.D., director of sex education for the Sinclair Intimacy Institute. "People who have a good sex life feel better [mentally and physically]."

"Sex can be a wonderful cementer or a terrible wedge" for relationships, says Dr. Linda Banner, Ph.D., a licensed sex therapist specializing in marriage and relationship counseling and a researcher associated with Stanford University Medical School.