Distance as a Guard

I just woke up with the realization that I probably come off as a distant person.  The sad thing is that it's not intentional.  This came from several attempts at putting myself out there, and ending up disappointed in the end.  I don't want to put it all on the line, and receive that heart-break that so often follows.  From my experience, it seems to be that when someone knows how important he or she really is to you, the next step is to push you to your limit to find out just how much he or she means.  This person truly believes that you can't live without his or her presence in your life.  I promised myself that I would never give that impression again because ultimately two people end up disappointed- myself for wasting my time, and that individual because I'll only take so much.  If I leave with nothing else, I'll leave with my sanity and self-respect.