There are many possible causes of abusive relationships. Childhood issues, brain chemistry, significant life transitions, and societal messages are just a few. Whatever the source, abusive relationships function by virtue of one (or both partners) attempting to control the behavior of the other.
The solution is to learn to recognize how you might be doing this (it's often unconscious, unintential, and invisible if subtly or explicitly manipulative, intimidating/coercive, and domineering behavior is what you saw growing up and have been doing your whole life), and then to find alternative thinking and behaviors.
Sounds so simple, but it's much harder done than said and almost always requires some professional intervention and support. All too often, people will make a brief well-intentioned attempt to change their behavior but slide back into familiar, established if miserable patterns.