There are few exceptions to this rule and at the moment I can't even think of any! If you're faking it in any area of your relationship it's only a matter of time before it comes back at you and bites you in the ass.
Once you've faked it, you've painted yourself into a corner with only two options: staying in the corner or walking out and messing up the paint.
Here's a really good example of making things hard for yourself by faking it.
Have you ever been with a man you really liked but who you didn't feel connected to sexually? When you're with him you just don't feel the chemistry. So rather than telling him you're having a problem feeling sexual, you decide to fake sexual pleasure instead. You pretend he's a great lover and that you're sexually satisfied. But there's a catch, as you continue to see him, you have to pretend to enjoy sex every time.
Now your options are limited. You can't tell him you're having a problem without making him wonder what's been going on with you all along. So the only other alternative is to keep going on with the sham until you can't stand it anymore.
There's relationship advice that will tell you to "fake it till you make it," but in this case and in many more; it's like using a band aid to cover a deeper problem.
There is only so long you can fake it in this situation, eventually you're going to want more from your intimate experience with him but it will very touchy when you ask for it.
If you ask, he will wonder what's you've been feeling and when the idea that you've been faking sexual pleasure gets into his head it will hit him hard. It will be a blow to his ego and his manhood. The fact that you're now being honest with him will be unimportant. He will only be able to focus on the fact that you lied, and it will cut him deeply. You've taken away from him the opportunity to do better and work on the problem with you. He will begin to question your love and your loyalty.
Relationship Advice: When a man learns you've been dishonest in one area, he will begin to doubt you all areas.
Let's be honest, you fake it because it's the easy way out; the path of least resistance. The more you think you can get away with, the more tempted you are to find ways to make things easier for you. Rather than having the courage to tell him the truth in the beginning and do something about it, you avoid the truth out of fear.
There are many fears you have to face if you're honest: fear of being judged, being unkind or being wrong. But none of the those fears is worse then the pain you cause by betraying someone who cares about you.
My best relationship advice is to be honest in your relationships about who you are and what you need from the beginning. If you have issues in your relationship about sex, money, or lifestyle address them from the start. If you fake it you'll end up not only hurting your man, but you will be paying the price of living a lie and in the end not getting what you really want.