Your grandmother may have been onto something when she told you to just be good friends with that nice boy first. A recent study conducted at Brigham Young University's School of Family Life found that couples who waited to have sex had more stable and fulfilling relationships down the line. The couples in the study who decided to get it on after the first date or within the first month of dating seemed to experience the worst relationship outcomes. "What seems to happen is that if couples become sexual too early, this very rewarding area of the relationship overwhelms good decision-making and keeps couples in a relationship that might not be the best for them in the long run," researcher Dean Busby told Live Science. Translation: It's easy to fall for the nookie. Sex can mask all of the signs that he's Mr. Wrong, especially if you don't take the time to get to know him first. This may be what Steve Harvey was trying to say with his 90-day rule in "Think Like a Man, Act Like a Lady." But how many of us are willing to take that time? The study found that nearly 40 percent of couples get frisky by their second date.