As a guy being emotional can actually stop sex from happening altogether if the emotions are the wrong ones or as you suggested can be a great outlet for them depending on what they are and how they are affecting you. From what I can understand for girls it can just make it so it is not enjoyable or again be a great way to deal with your emotions.
In the end I think it comes down to what the emotions are, why you are having them and how they are affecting you.