Love & Honesty

Relationships are tricky through and through. They require continuous maintenance, time, and most of all patience. My relationships, especially lately, seem to be in limbo. Sometimes the longevity of the relationship clouds my judgement and I end up resenting the friendship. I guess I struggle with my compassionate nature because compassion and logic don't always go together.
To be frank, compassion is a very illogical emotion. For instance, I am not a rich person. to say the least I get by through God's grace and mercy. However, I am extremely generous, especially when it comes to me feeling compassionate. How can I give away the little that I have? Honestly, I don't know, it's like I'm compelled. The big problem with my "compassionate generosity" is I get taken advantage of. Sometimes it's deliberate, sometimes its not. The other problem is I tend to forget about the past when a new situation arises. Dumb huh? I know it is and I really do try and change, but here's my other problem, I like being compassionate and generous. And the relationships I have, platonic and other, are with individuals who know me well enough to know all of this about me.
So where do I draw the line? Ironically, this question I do know the answer to, at least logically I do. I draw the line when someone is blatantly taking my kindness for weakness. Yet the longer I am in these relationships/friendships, the harder it is for me to not only recognize this type of behavior (people can be very deceitful), but it's harder for me to get out of the relationship.
I was thinking about a pros & cons and a likes & dislikes list to help me weed out my life. but that seems sort of crass. I don't want to stop being a compassionate and generous person that my parents raised, yet I don't want to be bitter and distrustful either. I think it is really important for me to resolve these issues and maybe even dissolve some of the relationships/friendships that I have right now. Working on me, getting my mental and emotional state back on track is a top priority for me. Therefore I'm setting out to do something about situations where I have been or am being taken advantage of. But hey, that's just me.