1.Your partner repeatedly breaks your trust
Trust is the first on the list because it is the most important part of any relationship. It is the root of any stable and serious relationship and betrayal can really destroy it.
If a person continuously breaks your trust and you still trust them, it is their fault, not yours. Blaming yourself for trusting someone who betrayed you is very natural but you should never do that.
You are able to learn who is trustworthy by gaining experience, and you can’t learn without being betrayed. You get an important life lesson either way.