The first sexual encounter with a friend can be the most nerve-wrecking moment in the entire relationship. The uncertainty about the direction the friendship will take after that encounter is comparable only to that “should I call/sms/tweet, or should I wait for him/her to call/sms/tweet?” moment after a sketchy first date.
The situation is only made more awkward when you let them know that you did not enjoy sex with them. You did not initiate sex thinking it would be bad. The two of you have shared intimate moments before. They even watched Girlfriends with you and wiped your tears when Joan and Toni stopped being friends. Your conversations can go on forever. So, you anticipate that your bodies will speak to each other the same way. You expect your friend to already know what you want, what buttons to push, or rather how to play with your button. But then your sexual experience is incredibly underwhelming – how do you begin to address it?
Most people would rather not say anything “for the sake of the friendship”, which is perhaps the worst thing you could do.