A lot of the disconnect between men and women has to do with the fact that men have been socialized in a way that runs counter to the way women do things. This "masculine code" is something that women simply have to be aware of to interact effectively with men. Think of these beliefs as deeply rooted rules of behavior, part and parcel of what it means to be a man:
How This Affects You
Every single way in which the world makes a man is at odds with most women's definition of intimacy. Relationships in general, and intimacy in particular, are all about taking down your defenses. Intimacy means trusting people enough to give them the power to hurt you. And that is absolutely contrary to a man's nature.
What You Can Do About It
To help a man overcome his fear of vulnerability and intimacy, you have to demystify the whole area for him. He knows that his emotional self contains information that could potentially be used against him, so you have to convince him that he can trust you with it. Teach him that when he allows himself to be vulnerable with you, he can be assured of a good outcome.
Also, you tend to get what you give. If you're open and honest, and you reveal true things about your intimate self, you're much more likely to have that behavior reciprocated than if you simply demand that he do so.
We Hear You!