In my opinion, monogamy is something that you do so that the person you love lets you keep living with them, not because it's particularly rewarding for its own sake.

So a threesome always sounded like the perfect solution for partner-sanctioned cheating. But I didn't really catch the ménage a trios bug until about four years into my current relationship, when the boyfriend and I began actively seeking a woman to join us in the bedroom. I wanted to try something exciting and different to shake up our sex life, but -- I'll admit it -- I also wanted the good-girlfriend points amassed by participating in such an encounter.

After a few failed attempts, I finally drowned my nerves in roughly a gallon of wine and propositioned a similarly soused friend while sharing a cab home from the bar. We called my man and told him the good news (His response: "I'm sleeping") before stripping down and slipping between the sheets of our shared queen-size bed.

Click here to read what they don't tell you about threesomes ...

I didn't feel any jealousy when my boyfriend started to make out with my friend, more just a general awkwardness about what exactly I should be doing. What they don't tell you about threesomes is that the whole thing is sort of like an awkward game of sexual Twister except without anybody telling you where to put your hands.

I was also nervous about how intimate I should get with our "guest star"'s naked body. I had had enough barroom liplocks with other girls to be pretty comfortable in make-out/groping territory, but when she started to head downtown, it was somewhat ... unfamiliar. I rolled with it for the sake of experimentation, but as a primarily heterosexual woman it was definitely more novel than arousing. But there was something extremely hot about meeting my boyfriend's eye while entangled with another woman.

When we had all "finished," we collapsed in an overheated heap and congratulated ourselves on a job well done. Had my threesome experience ended here, I would have given it at least three and a half stars. Unfortunately, it didn't end there.

You Know What They Say About Guests and Fish ...

When I tried to pull on a tank top, our guest star loudly protested, proceeding to spend the next half-hour groping me while I tried in vain to get at least a few hours of sleep before the sun came up. As grateful as I was for her selfless participation in our bedroom fantasy, once I'm done, I'm kind of done, you know?

My lack of interest apparent, she moved her amorous attentions to my boyfriend, who unsurprisingly, reciprocated. They cajoled me to join in but, tired and grumpy, I gave them the go-ahead to carry on while I slept. When I awoke from my less-than-satiated slumber a few hours later, the bed was empty and they were in the living room having eggs together.

The Aftermath, and What I Learned

Even though I had given permission, the whole thing seemed a breach of sexual etiquette. Maybe it's stereotypical, but I didn't blame the guy as much -- he had never done anything like this before. I really don't think he understood the distinction between being encouraged to sleep with another girl at night and not being allowed to sleep with her the next morning. But I feel like any woman understands that being invited into a couple's bed evokes a kind of sacred trust. You can do it together, but you really shouldn't do it alone.

In retrospect, I would say that while sexy spontaneity was fun, ground rules and planning are also important. Had we talked about what we were doing beforehand, my friend would have clearly understood my expectations, my boyfriend would have known what was cool and what was off-limits, and we both probably would have changed our "Outer Space"-themed sheets and bought bagels in preparation.

Emily McCombs often chooses sandwiches over sex and is an editor at Lemondrop and its brother site, Asylum.