The idea of no strings attached sex with an opposite sex friend may sound like a good idea, but in real life, not to so easy to pull off. Hollywood has started a trend in casual relationship movies, first with No Strings Attached and now Friends with Benefits starring Justin Timberlake and Mila Kunis. But do these relationships work in real life? The fantasy sounds simple, but real feelings usually make things messier. That is where the whole idea starts to wobble.

We tend to romanticize casual relationships, thinking we can turn our emotions on and off like a faucet. The reality is more complex: one person could develop feelings for the other, upsetting the balance of “no emotional investment.” When you are in a sexual relationship with someone, how can you predict emotions will not play a role? Usually, there isn’t a Hollywood ending and someone ends up hurt. The arrangement can feel easy at first, but it rarely stays that way.

This is why it can be hard to stay friends with someone when the benefits go away. The relationship will change. Can you handle your friend moving on? Consider your own tendencies and jealousy before you engage. Before anything starts, it helps to ask whether you are really prepared for the emotional fallout. A little honesty now can prevent a lot of awkwardness later. Sometimes the bigger issue is not the setup itself, but what happens when it ends.

Following are some questions you can ask yourself before you get involved in a “friends with benefits” relationship: Am I looking for a long-term relationship? Can I handle my friend wanting to be with another girl? Can my friend handle ME wanting to be with someone else? The key is making sure you are both on the same page and that you keep the lines of communication open. If either person is hoping for something unspoken, trouble is probably coming. Communication is key.