I have been in several romantic relationships that ended badly.
romantic love is a strange thing
It is, is there a psychological reason for this?
i think humans have a desire for intimacy
Do you know if any humans don't have a desire for intimacy?
-avoidant
Investigators have explored the organization and the stability of mental "working models" that underlie these attachment styles. They have also explored how attachment impacts relationship outcomes and how attachment functions in relationship dynamics.
Extending attachment theory.
Mary Ainsworth and John Bowlby founded modern attachment theory on studies of children and their caregivers. Children and caregivers remained the primary focus of attachment theory for many years. Then, in the 1980s, Sue Johnson began using attachment theory in adult therapy, and then Cindy Hazan and Phillip Shaver
Intimate relationship
An intimate relationship is an interpersonal relationship that involves physical or emotional intimacy. Although an intimate relationship is commonly a sexual relationship, it may also be a non-sexual relationship involving family, friends, or acquaintances. 
Emotional intimacy involves feelings of liking or loving one or more people, and may result in physical intimacy. Physical intimacy is characterized by romantic love, sexual activity, or other passionate attachment. These relationships play a central role in the overall human experience. Humans have a general desire to belong