In the beginning stages of a relationship, it's sometimes so easy to be hot-and-heavy that having sex on the regular is akin to breathing: It's necessary for survival. Then life sets in and sex can be the last thing on your mind. "Most couples today are juggling busy schedules and sex doesn't feel a priority," relationship expert Andrea Syrtash says. "The issue is that if you don't use it, you lose it. The less you have sex, the less you may desire each other. So, it's essential to keep up intimacy in your relationship."