So what is the biggest sexual problem these days? If you are single and looking for a date, you might think the biggest problem is just getting the opportunity to be sexual with someone--somewhere, sometime. You probably can't imagine that sex would ever get boring. But, sad to say, I'm here to tell you, it does. In fact, it can get so boring that couples start wanting to have sex less and less-and then, not at all.

Granted, this rarely happens when two people have just fallen in love. At first, the newness and uncertainty of the relationship are usually enough to make even a slight touch an aphrodisiac. But when couples have been together for a long time, sex can easily become uninteresting--even for partners who are reasonably happy together and would still say they are in love.

What causes the disinterest? Here are, in my opinion, the seven most common factors:

Back-Burnered Sex

At the beginning of a relationship, almost nothing is more important than being able to touch, kiss, and make love. But priorities change. After a while lovemaking may fall behind career, social commitments, TV, or the simple need for sleep. Even answering e-mail may take precedence. How can passion stay alive when it is treated like a second-class citizen?

Efficient Sex

After a while, partners learn a great deal about how their bodies respond sexually. And, given that time is precious, they may use this knowledge to achieve or give a fast orgasm. This can make sex very efficient. But by eliminating playful experimentation, it can also make sex boring. It can become a matter of touch here, touch there, a few appropriate thrusts-and on to another project.

Predictable Sex (routines)

In some areas of life, predictability is wonderful. For example, you'd love to plan a picnic with confidence that it won't rain. But most things lose their allure if you can predict the beginning, middle, and end in exhausting detail. If couples get into a rut--with the same foreplay, at the same time of night, in the same way--is it any wonder they cease to get excited? Think of it this way: Steak is great-but if you have it every night, you will stop looking forward to it. You might even sneak out of the house, looking for some chicken...

"Safe" Sex (no risk, no growth)

I'm not talking about contraception or disease prevention here. I'm talking about risk-taking that is constructive (and not dangerous to your health). Sex gets boring if there are too many things that are never even considered, much less done. For example, it would be understandable if a partner is somewhat conservative and wouldn't chance making love on the beach-understandable, but not much of a turn-on. If, however, one day that partner, out of the blue, throws caution to the wind-what a turn on!

Lazy Sex

Sometimes great sex requires some "athletic" efforts, or a lot of time spent in foreplay or oral sex. Partners who do the absolute minimum for each other are lazy-and each person knows it. This lack of generosity may grow, each person taking his or her cue from the other. Pretty soon any effort seems like too much bother.

Unattractive Sex

If partners stop trying to look great, smell great, and feel great to each other, sex gets less pleasurable and less interesting. It's odd that couples tend to put the most work into themselves in the early part of a relationship when they need it the least, since lust and newness will go a long way all by themselves. By contrast, some years later a little artifice and seduction are really appreciated-maybe necessary as well. So it's sad when, by this point in the relationship, the two partners have slacked off.

Unemotional sex

Sex gets boring if nothing is at stake--no deep emotions, no reconnections, no praise, no verbalizations about how great everything feels. The connection becomes less intense without eye contact and without deeper connections between the souls of the two people. Long-term relationships need to give each other reassurance that their emotional tie is still alive, still reinforced by great sex. Otherwise, sex may seem to one or both parties to be just a matter of "going through the motions."

Can these problems be solved? Absolutely. Will they be solved without being conscious of them and working hard to avoid these pitfalls? Unlikely. If a couple has a sex life that is still intense, still worth rushing home for in the middle of the day, you can bet they are both trying hard to keep it vital and passionate. And that it isn't impossible to achieve. If it's important enough to both of you, you can make the effort to do it right.