Globally, it's accepted that about 50% of first marriages fail. What's even scarier is that these percentages increase dramatically in multiple marriages. There are many theories as to why this is the case. Here are a few possible reasons why couples who remarry are unable to make a success of their marriages:
People enter into these marriages still carrying baggage from the past. If you don't sort your issues out, you are merely going to burden your new partner with these issues. You will keep on making the same mistakes that you made in your previous relationships.
Marrying on the rebound is another reason for marriages failing. You get married because you and your partner love each other, not to fill a void that is left over from your previous marriage.
Women are more independent now than ever before, and men are becoming more self-sufficient in the domestic area of marriages. This means that most parties go into marriages feeling that they need to protect their turf which in turn can lead to squabbling and bickering.
Most people have kids during their first marriages and like it or not; children can be the glue that keeps some marriages together. Fewer people have children in their second and third marriages, so they don't have that glue to keep them together during the tough times. Another effect of not having children is that there is no burning desire to keep the family together for the sake of preserving the family.
In some second and third marriages, there are already children, and this presents added strain of parenting some other person's children. Children may not take to the new father or mother, and this presents its own set of problems.
There are some people who leave their baggage at the front door and go onto to enjoying a happy and successful second or third marriage.