I honsestly believe the number one cause for divorce is and always has been (selecting the wrong mate). This happens because many people get married for the wrong reasons. Oftentimes they are too young or haven't figured out want they truly want or need from a life-time partner or they didn't invest enough time to get the know their mate in order to determine if they truly have the same value system and (agree) on the major things in life. Poor planning education/career decisions adds lots of pressure.
There is no amount of "communcation" or "work" that can overcome being with someone who does not want what you want.
In other instances they let circumstances dictate why they got married ( having a child, all my friends were getting married, a goal to be married by a certain age, had been dating for years and felt it was "the next step", someone was given an ulitmatium, the sex was off the charts, was tired of being single...etc)
A marriage based on circumstances rather than love is likely to fail.
Last but not least each of us is entitled to have our own "deal breakers". Hopefully both people have shared those with one another before they got married. If cheating, phyiscal/verbal abuse,drug/alcohol addiction, irresponsible spending which leads to bankruptcy/bad credit/eviction/foreclosure, physical neglect...or whatever. The bottom line is each of us is responsible for our own happiness! Much of your happiness is determined by your choices/decisions of who to allow into your life and how much time you choose to invest being with them. All relationships are "at will". It's our fault if we choose to stay with "toxic" people.
A divorce is nothing more than one or both people reaching the conclusion that they made a (mistake)! In any other area in our lives we would be applauded for attempting to undo or correct an error. Marriage is one of the few instances where we tell people to learn how to "change water into wine" or "fit square pegs into round holes" and you are (obligated) to stick to a decision you made possibly at age 18, 19, 22 for the rest of your life as if people NEVER make a mistake and marry the wrong person or learn they no longer share the same values.
The only reason I can think of to "try harder" is if both people are "in love" with each other and still agree that they want the same things for the marriage as well as agree on a strategy to have those things. Of course if that were the case the marriage would probably not be in trouble!