In all honesty I do not believe anyone on their wedding day is (planning) to get divorced. The number one cause for divorce is and always has been (selecting the wrong mate) for ourselves!
This happens for a variety of reasons. Among these are we don't know ourselves well enough to determine what we want and need in a partner for life. This is often the case when we get married too young. We simply don't have enough (life experience), completed our education or established a career path to support a marriage and family. Other times we get married to people before we (really know) them or we get married due to "circumstances" (accidental pregnancy, tired of being single, all of our friends are married, we had a pre-determined age goal, the future spouse had assets/income we placed a high value on, they treated us like a king/queen and didn't ask for much in return. (Which we thought was good since we were not "in love" with them.) we'd been in a relationship for years and just said, "What the hell, why not?"
As I stated earlier there are countless (WRONG) reasons why people get married or marry the wrong person. Not long ago I wrote a hub regarding 5 reasons men should NOT get married and they would also apply to women. No one I know of enjoys daily fights/arguments. Lastly people have been known to change overtime. What worked for us at age 25 may not at age 45. There is no neutral. We're either growing together or growing apart. http://hubpages.com/relationships/5-Reasons-Men-Sh...
There only two ways to experience joy and peace of mind in marriage/relationships. We either get what we want or we learn to be happy with what we have.