It's common that men change after marriage, I don't know why they become nervous and indifferent at the same time. They were so soft with her but after getting married all this change into aggressiveness and passivity... why?

No, they change before marriage to "get the girl." After marriage, they revert to form.

Actually all (most) people change as we age and meet new changes in our lives.

Next often it is not as much that they change, but the viewer often is too in love to see it.

A change of character often hides a problem. It could be the feeling of entrapment, boredom in the marriage [couples do change after dating], feeling sexually deprived, it could be a number of things.

MRS.S

I agree with the above posters, however, I don't see this as only a male issue... I have seen it from both sexes and have experienced it personally...

But to address your question about men I would say that many things may apply.

In addition to what has already been said;

A sense of loss in some freedoms.

Immaturity

A sense of sudden additional responsibilities

Financial problems

Problems 'adjusting' to the change in life style

To only mention a few... more.


Stringer

The words "most" and "men" in the title are not accurate. "some" and "people" are much more accurate. This is not an issue exclusive to men and its certainly not most men.