To my mind the single biggest issue is the relationship itself. If the 2 parties have love and mutual respect and are truly committed to the marriage then it will be strong enough to survive these kind of challenges.
If there is distrust, a lack of respect and a lack of commitment to the marriage then it will not survive challenges.
I have blogged about this before and you can read the full article there (see my signature for the link). The article is titled 'On acceptance and appreciation' if you are interested.
