How would you interpret this statement?

"We know you better than you THINK we do. And everything we do has a purpose. Manipulative, maybe, but with a purpose."

Well that wasn't verbatim, but I don't remember. *sigh* I thought I'd at least be dating before relationships got this hard.

How do you know when to leave someone? How do you know what will last and when to stick it out? Where is the fine line between trust and standing up for yourself?