Advantage

I'm working on my step work today.  I'm on the 4th step: Made a searching and fearless moral inventory of ourselves. 

My sponsor gave me a series of worksheets to help in completing my inventory.  They ask me to make 4 lists and answer a number of questions about each one. 
1 - Things I am afraid of; people, places, institutions, principles, etc. 
2 - Things I am resentful towards; people, places, institutions, principles, etc.
3 - People I have harmed through action or failure to act.
4 - List of sexual experiences, with whom, what we did, and who was harmed. 

I started on my resentment list today.  It's long.  As I went back to start listing the cause, I noticed a pattern.  I'm angry because I feel taken advantage of.  And not in just a few cases, but in almost every case. 

Take Advantage: capitalize; derive a benefit from; make excessive use of; impinge or infringe upon;   Synonyms: exploit, milk, step on, use, use for one's own ends, impose upon, deceive, betray, ensnare

I was just thinking the other day how insecure I feel:
"You know someone is taking advantage of you when you do not feel safe with them.  Anytime there is a question about some one's motives, that is an indication that you cannot trust that individual.  People who care about you won't try to take advantage of you and you will feel secure around them."
(wiki.answers.com)

This describes my relationships with my sisters exactly:
"If you are being taken advantage of unfairly, it's possible you are dealing with a narcissist.  The narcissist believes she is the most important person in the world and does not care about your feelings, which is why she takes advantage of you.  In her mind, your needs are dramatically less important than hers because of her imagined superiority, so she doesn't see it as taking advantage at all.  She feels entitled to your kindness because she is better than you and everyone else, as far as she is concerned."  (ehow.com)

I want to be kind. I want to help and serve others. I feel like that's what the Lord would have me do. Yet, in almost every instance I feel like my kindness, thought fullness, and love was taken advantage of.  How do I make it stop? How do I remain true to myself and stop others from taking advantage of me?  I don't know how to do that.