We're all creatures of habit. If you've been with the same partner for a long time, you've probably settled into a comfortable routine: A little kissing, a little foreplay, and the same sexual positions. There's certainly nothing wrong with familiarity. Couples usually make love in the same ways because they like the way they feel. On the other hand, sexual ruts can be a real stumbling block if they arise more from routine than from real desire. A lot of the how-to sex guides seem to assume that every man has joints of rubber and the strength to stand on his head, caress his partner, and have mind-blowing sex all at the same time. In real life, though, few of us have the energy (or the interest) to turn the pursuit of pleasure into bedroom gymnastics. What you can, and should, do is occasionally shake things up in bed. Novelty is a tremendous aphrodisiac.