All of us have our own sex fantasy, and this helps in actual sex. Sex fantasy can help you in masturbate but in real sex, how is it going to help. You see, most of us are trying hard to please our sex partner hoping to give him or her an orgasm. You may even trying to look conservative than usual. So when you try to hard in that, you are less focus. The things that you should do is treat yourself as in those porn movie, and think yourself as the whore in the porn video. Enjoy the sex like you are the whore in the porn and this will make yourself arouse and increase the desire in you and your partner. When you get to do this, you will turn the beast in your sex partner and release the sex devil inside him or her.
Another common situation in sex, no matter girls or boys do the same thing. They will try to suck in their tummy in so that they look slim and fit. What you don't know is the air is helpful for orgasm, deeper breath may be more easy to have orgasm. When you suck in your tummy, your breath is not as deep as usual. So relax, be yourself, your partner know that and he or she can see it, don't worry to much and try to focus in the sex and enjoy it. Throw yourself inside the sex and let it all out, your sex partner is going to amaze by you.