Even though the answer is not yet proven, at least now I can stop thinking about it...
All this while, I've been thinking of this one of the God promises:
'good men are destined for good women and bad men are destined for bad women.'
I can't see the fairness in that promise. how about those 'bad' (I don't know the suitable word to describe jahat) guys or girls who wish to become better if they are destined for people with the same attitude? I don't dare to think further, fearing it would undermine the iman. but the previous discussion with some sisters of mine had given me at least a point to stop doubting the promise.
The discussion came to a conclusion, what is mean by good for good and bad for bad is not necessarily applied to a couple in the same time from the beginning. It may be described as the changes in a person when they have been living their lives together. (I'm trying to put the sentence in a clear way T_T )
What I understand is, a good man, who supposes to be destined for a good woman as well, might be married to a bad woman in the first place. when they are married, it's the man responsible to guide the woman into the right path. By means, in the end, both of them will become the good persons.
But if he fails to guide his wife, following the other side of the road, both will end up in the wrong path. which satisfy the later part of the promise.
And same goes to a good woman who marry a not-so-good man. the responsibility to guide the partners apply to both genders.
It is possible, some people start well from the beginning until the end. praise to God.
Don't worry of not being good enough for a person. you can marry a pious even though you are not a pious man or woman, if God willing, because s/he might be the person who will change you!
my grammar sucks...ooh laa laa.. (trying to defuse the situation) jangan la serious sangat, nanti menangis. :')