Most Helpful Guy
Lack of trust for each other. Lack of conpromise. Lack of clear communication or lack of communication. Unwilling to cooperate and work together on the relationship, mistakes and fighting can and will happen but both parties must be willing to forgive each other and keep moving forward and not constantly holding grudges towards each other and constantly blaming each other. Having unrealistic expectations and goals for the relationship and as well as for themselves and their partner.
Also, the younger someone marries the less likely the marriage would last long the last I've checked. And then sometimes it takes a second time or third or more before they finally found each other to be a perfect fit for each other. Other times they don't and it never fit or ever works out no matter what.