While people are imperfect, some choose to stay that way rather than do the work of becoming a better person. They get into a relationship, and they spend the first months ensuring their faults do not show. These people often have addictions such as drugs, gambling or drinking. They may stay straight and sober until their significant other has made a commitment. This is when the addictive person relaxes, and they then let their addiction take over.
When a person is suddenly faced with an addicted partner, they may give them a second chance, and the other person might even take the opportunity to change. Many addicted partners are not interested in changing. In the past, they have found that partners who will give a second chance will often give them many more chances. Rather than overcoming their addiction, they simply keep their lifestyle until their partner ends the relationship.