Yes to both. It is always OK to say no – ALWAYS. Being pressured to have sex when you aren’t in the mood is never sexy but there are some exceptions. There is never a black and white answer to this question. With that said, it’s important to understand why you aren’t in the mood. Is it because you are in pain or exhausted? Or are you just preferring to watch TV? Or maybe you aren't having the type of sex you want to be having and therefore deciding to decline? Once you understand why you aren’t in the mood then you can make a more informed decision as to whether or not to decline your partner’s initiation.
Sometimes, it can be helpful to accept the invitation to connect sexually. If you can muster up the strength it’s likely that once you start engaging you will enjoy it and the positive connective tissue will increase. In loving relationships we all do things that we don’t necessarily want to do. Whether that’s having pizza for dinner when you want something else or watching a TV show you don’t particularly like. Sex isn’t any different.