I think I read somewhere that the therapeutic relationship is defined as goals plus rapport. The goals bit is important--I'd need to work with a T who agreed with my goals and who I felt helped me to achieve them--but I also believe it's somewhat less important (or at least less "special") than rapport.

Maybe rapport is what we mean when we talk about the quality of the relationship. I think it's built over time--you get a particular "vibe" from someone and go on to test boundaries, give them the opportunity to "prove" themselves, take leaps of faith, and so on.

As to how you appreciate the relationship for what it is instead of wishing it were something it can't be...maybe part of that has to do with how "well" you're getting. I noticed that when I started communicating better with people in my life and getting wants/needs met through them, I craved that much less in the therapy hour.

Maybe part of it is also experience and recognizing places/situations where the therapeutic relationship is actually better/more helpful than a friendship (or whatever "more" it is you wish you had with your T). For me, I much prefer talking to T about certain difficult issues because I don't really have to deal with his reaction like I would a close friend's. That is, where a friend or family member would have the natural impulse to respond to something terrible with an emotive "That's terrible!" T's don't do that.