Well, the answer depends on how you touch and how you have sex.
If you touch like, A LOT, and always use the exact same technique, then you can be training your body to only respond to one kind of stimulation. This is a problem more common for men than women. If they grip too hard when they are enjoying themselves, then they get used to a stronger pressure than a woman's body can possibly provide. The answer in this case is not to stop masturbating, but to vary your technique so that your body doesn't get stuck in a rut.
The other thing is, there aren't a lot of women who can have [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] by vaginal intercourse alone. This is because the [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse], where the woman gets the most pleasure, isn't located inside the vagina. It's on the outside. So if it gets to be your first time and your guy just hammers on you for awhile and then pulls out, you probably wouldn't [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] whether you had been masturbating or not. The way to get around this is to use lots of foreplay first, use lubrication, use positions that stimulate the inside of the [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] (I've found that from behind works best for that, but can be difficult to do if you are not perfectly sized to each other--pillows help) and get your guy to put his fingers or one of your sex toys (if you have any) to work down there while you are making love.
Most couples don't come at the same time. If you come first, well, just keep going. If he comes first, make it clear that you expect some continued attention. He may be soft, but his fingers and your toys aren't. When my fiance and I make love, it is often the case that I get my [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] after the official 'sex' part is over.
And also, don't feel pressured to have [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse], fake or otherwise! Sex can be a very enjoyable activity even if you don't climax, and that's fine too. Women may be able to have multiple [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] in a row, but ours are much rarer than men's. And hardly anyone gets to [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] the first time they have sex, what with it being kind of ouch and all. (Though with lubrication and plenty of foreplay, it won't hurt any more than getting pinched on the arm.)
And you can put your mind at ease--with the right partner, sex is MUCH better than masturbation. If the sex you're having isn't more enjoyable than doing it yourself, then you either need better communication or a different guy.
It's a bit like getting a foot massage. Sure, you can rub your own foot because you know exactly where it needs to be rubbed, but doesn't it feel better to have someone else do it?