i actually prefer the term "boundaries" over "limits." to me, "limits" have a somewhat "lacking" connotation, like "it's up to this point, but no more." for me, i'd focus on what things can't be (as in, what's "above" the line of limitation), rather than what they are (like the glass being half empty as opposed to half full, i guess).

"boundaries," in my opinion, is a more "inclusive" term, like these are the lines that contain the relationship (rather than this is only how far it will go - as in the limit), and are what keep it safe and healthy.