People in long term relationships tend to get into a rut, and they fail to examine their lifestyle in any meaningful way. Some of them are simply used to their current status, and change requires too much energy. Relationships that have lingered long past their usefulness are often ones where people see nothing too wrong, but they also know nothing is really right with their life. They lack the motivation to make major changes on their own, but life has a way of pushing people into making changes.
While tragedy is often a catalyst for making major life decisions, this does not always have to be true. Sometimes it is something as joyful as a friend having a baby, or a parent pursuing a new career that makes people examine their life. These are events which give people an opportunity to open their eyes, and they sometimes see their goals are not being met with their current partner.
Beginning a family is a major life decision, and it requires an enormous amount of commitment. Partners who have been together for years may disagree whether or not it is time to begin a family, and this can cause a rift in the relationship. If only one person is eager to begin a family, they may find their partner is not willing to remain with them.
Major life changes of close family members have also been an eye-opener for many couples. If parents choose to leave stable employment and open their own business, this may give their adult children a new look at their own lives and relationships. An adult child may see their parents' enjoyment and wish to follow in their footsteps, but their partner might believe steady employment is more important. If the two cannot find a middle road through this type of situation, it may permanently scar the relationship until it ends.