Theres an excellent book call "The Human Magnet Syndrome" written by a guy called Ross Rosenburg.
Basically he explains that we are all on a spectrum. At one end the are Co-Dependents and at the other are Narcissists/Sociopaths. If you are high on the narcissistic scale you are usually attracted someone who is high on the Co-Dependent scale and visa versa..kind of like balancing out each others personalities/traits etc and subconsciously we are automatically drawn to one another.
People who display Co-dependent tendencies/traits have weak boundaries, don't like saying no, upsetting people, like to please others, put others before them selves, see themselves as fixing others. This usually as a result of the way their parents were and how they were brought up, sometimes their parents were narcissistic, alcoholics and to the co-dependent this seems normal.
Sociopaths and Narcissists have similar dysfunctional childhoods, but these manifest themselves in entitled, selfish, manipulative behaviour and lack empathy etc...
If you've been in a relationship with a sociopath and escaped only then do you recognise what you've been through and can look for answers, validation etc..Co-dependent people do have the ability to recover and learn to work on boundaries etc, and the fact that you can recognise that you have been attracted to a certain type of person is a good thing. This allows you to work on yourself and set boundaries, find out that it's ok to say 'no'...
Sociopaths and Narcs are so self absorbed and entitled that they fail to recognise that they may need therapy and so they often go from relationship to relationship following the same patterns.
They Love-bomb there victims -This is what you describe as everything seems so perfect, things happen very quickly, the appear to 'Get You" be your soul mate etc..It's all an act to hook you in.
They Devalue you after a while, usually subtle manipulation, make you fell insecure, gas light you.
Finally the Discard If you discover what they are, call them out, leave them they discard you with great ease, like you never existed, find a new partner really quickly.
Sometimes they can try and get you back by "Hoovering" you...everything is done to draw supply (attention) from you, good or bad it doesn't matter to them, they need this supply like a drug. Maybe see it as the good attention (Love and praise) they get from you is like pure heroin. If they can't get this they'll make do with negative (Rage, provocation) attention = Methadone.
Recognising that you seem to be drawn to these types is the first step in your recovery and allows you to fix your picker. See the red flags and run for the hills if you see them.