Sentence:  Could it be, that way back, early in this relationship, consciously in my mind, I chose to set a boundary or to <WSD>"draw a line in the sand</WSD>" between this person and myself? This line meant that I would not allow the person to come any closer to me, or my "seeming secrets", than that line in my mind. 
Meaning of the word marked with <WSD> tags:  To create a real or artificial boundary or distinction between (two places, people or things).