Thommy wrote>>>more than anything i want to end this cycle of subconscious self-destruction in relationsips... but how? i've asked myself over and over again>>
Have you considered finding a good counselor to help you work through some of the questions you have? Also, there are several good books out there that deal with the questions you've raised. One that comes to mind right off is "Facing Love Addiction." In this book the author talks about how we pick people who aren't the best choice for us, or we keep going back to destructive relationships, and why we do that.
There are a few other's that I remember reading but will have to look those up. Sometimes we find the answers to "why" we keep repeating the same patterns over and over when we dig really deep to find out "what" started that pattern in the first place. And we can't change that pattern until we recognize what's causing it.
You're here asking questions, and that's a good step. 
GT