It’s always best to treat each new relationship as a clean slate, if you bring old baggage into the new then you are saying that you expect it to be the same and every relationship and person is different. Also you often get what you expect.
There are always lessons to be learned in life and if you keep going for the same person who tends to let you down or treat you badly then it could be that you are not listening to your inner voice, is it because somewhere deep inside you think you deserve this? Is it a pattern of behaviour and expectation that you have inherited from your parents?
Before you tar every potential partner with the same brush, clear out your old thoughts, behaviours and patterns and step up your thinking and expectations, you will soon attract the kind of person that matches you and you can be happy with.