Secret of a successful marriage

As I was discussing with a friend about my most recent post(Case No.1),
she tells me the secret to a successful marriage is by removing 'divorce' or
'separation' as an option.
- Another friend argues that it is the secret to a successful marriage and not
for a happy marriage.
- Another says learning to compromise and improving tolerance will lead to more
understanding and that is the secret for a happy marriage. Just eleminating the option of divorce alone will only make the marriage more mechanical.
- While another says "Just live in the present" and do not dwell upon the past.
Personally, I would go with the last one as it works.
As far as the last but one option goes, it does sometimes save a failing marraige though it could prove extremely stressful for the compromising spouse.
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Now,which of these could help the couple in the Case No.1