There’s a reason why you and your wife of 20 years don’t ravage each other anymore, and it isn’t for your lack of trying. According to a new study in the Journal of Sex & Marital Therapy, women in a committed relationship report lower levels of sexual desire over time—a .02 percent decrease every month—while a guy’s desire stays the same. (Yet another reason to start with a lusty woman to begin with!) “Some research suggests that somewhere between 6 and 30 months, relationships switch from passionate to compassionate—more affectionate than ripping each other’s clothes off,” says lead study author Robin Milhausen, Ph.D., a sex researcher at the University of Guelph in Ontario. So are you to blame for her lack of lust? Not necessarily, Milhausen says. “For women with a lower sex drive in the first place, the switch to a deeper emotional bond may reduce some of the excitement associated with sex in new relationships.” Still, you’re not exactly helping matters. We asked several sex experts to shed light on the worst things you do around the house and in the sack that turn her off. Vow to never commit the following mood-killers again—try to Banish These Bad Habits, too—and your sex life will suffer no more. Ignoring Her Appearance “Guys in long-term relationships tend to stop noticing when their partner looks pretty, and so much of female sexual desire is tied to a sense of self-esteem,” says Ian Kerner, Ph.D., sex counselor and author of She Comes First. The fix here is simple: Pay her a few simple compliments every day, like letting her know she’s sexy, Kerner says. Putting Her Under Pressure Don’t worry or question her about getting orgasms, says Marnia Robinson, author of Cupid’s Poisoned Arrow. Stay relaxed and focused on playful touching, she advises. “This means no performance pressure on either of you. Let whatever happens happen in its own time—or not. Good sex is about connection and sensual satisfaction, not number of orgasms produced.” And here’s a nice added benefit to staying calm: “The relaxation is good for erections,” says Robinson. Using Porn As a Benchmark It’s good to keep the sex hot—but it’s more important to keep it real. In other words, forget that cool move you caught on XTube. ”Just because you saw a sexual practice in a film doesn’t mean it’s safe or satisfying,” says Robinson. And it might not even be something she’s into. “If you need extreme stimulation to perform with a partner, you may want to cut back on overstimulation. A desensitized brain can also find sex less arousing. As you restore your brain to normal sensitivity, regular sex behaviors become enjoyable again.” Time to rediscover the wonders of the missionary position. (Need more help finding great moves? Use our handy Sex Position Master.) Leaving Her Lips Hanging As men get comfortable in a relationship, their approach to foreplay tends to focus on the moments leading up to sex, says Kerner. “But female desire doesn’t operate like a light switch that turns on and off—it’s more like a dimmer,” he says. Small acts of intimacy like hugging and kissing can get her in the mood. But don’t get antsy: “Don’t expect her to be immediately turned on,” Kerner says.