There are many people who seek out a partner to make their life perfect, but few of them realize it will never really happen. They see the other person as someone who will take care of everything difficult, and they are disappointed when relationships keep failing. Happiness with self and life is something each individual must bring into a relationship with them because a partner is not able to provide this basic human need. Those without it will never be able to capture it for more than a short time if they expect their partner to always provide it, and it is this lack of balance that stops both of them from building a life together.
Relationships are not always equal, but it is to be expected. There are many times when one person loves the other more, and some people are better at caring for a loved one. Partners can live quite happily in this manner, but there must be a foundation for each of them outside of their relationship. If one person is unable to get through life on their own, they will drag the relationship and their partner down. This is often the reason co-dependent relationships are miserable.
Drama is something many people create to make their lives more interesting, but it can wear a person down. If one partner is always in crisis, their partner is left to cope with fixing the issue. Tired is often how the responsible partner feels, and they might eventually decide they would rather have a dull and easy life than stay with the relationship.
Equality in a relationship does not mean each partner has the ability to handle everything alone, and leaning on each other is part of the reason to have a relationship. For each weakness a person has, they must also have a strength that will contribute to their relationship. There must be a balance between the roles, or the relationship is doomed.