No, unfortunately that "love is enough" thing is a big fat myth :(
You'd probably find some interesting reading on this site: www.baggagereclaim.co.uk/
(This article might be particularly interesting?)
I've been with someone like this, kept going back even though I knew he was bad for me, etc. I used to say he was addictive - and he was! In the end I realised the bad times were outweighing the good, so I ended it, but it was really hard to do, and I did end up going back for one more time before I cut him out for good (while I was with someone else 
- learned from that not to get into a new relationship if not over your ex!)
It took me a long time to get over that relationship, even when I thought I was over it, I was so vulnerable at that point that I got into a relationship with someone who was really unhealthy, who was actually controlling and emotionally abusive. The addictive ex might have hurt me emotionally, but he was always honest and upfront about what I could expect from him, and he never used mind games to keep me from leaving. I still think of him fondly, even though I know if I met him for the first time now, I'd probably think "What a loser!", and if someone told me their boyfriend was behaving how he did to me, I'd be shocked.
If you know they are unhealthy for you, it never ends well. If you have children involved, you really seriously need to break the cycle asap. If it's just you, then it's your choice, but you probably will end up getting hurt... so it's whether you want to hang on until that happens, or keep the good memories, but then have that feeling of wondering whether it could have worked. (It never ever would have worked, FYI, but unless you do some serious work on yourself you probably won't really deep down believe that.)