i agree with fdg. it seems less to me to be about "the one" and more about the best of all possibles. it's the whole e7 strategy, but it's less about getting stuck in pain (and needing to keep as many options open as a result) as it is in getting stuck wanting something else with all the intensity of an sx type and being in a position when it's not possible to go after what you want (and thusly feeling deprived of what you feel like you are entitled to, your want, that you overidentify with). sx types are ambitious, willful, competitive, and want what they want, and being disconnected from that makes sx types feel inauthentic. but, at the same time, it's kind of bullshit too. the good thing about sx is that it is willing to incur personal risk in order to go after what it wants, regardless of what other people expect. the bad thing is that it often doesn't really listen to others and their needs because the only thing that matters is what I want (and what i want RIGHT NOW, in this particular moment).
to me the idea of 7 sx being consumed by "the one" seems mostly out of touch with the 7 sx types that i've met. my best friend is a 7 sx, and while the mental connection is probably the best i've ever experienced, the amount of space necessary is also pretty damn significant. because we are both very independent in our interests, even tho they intersect so consistently. while it's easy to reconnect and just get right to it, to feel immersed almost immediately, i can't really imagine how this plays out in a significant other relationship especially with another sx type. when both people feel that their individual paths are far more significant than making the sacrifices necessary to share a path. i think, for 7 (exxps), it's probably not until the tertiary really kicks in that a real choice is even viable (as a long term choice, i mean), at which point, the person can develop a larger kind of goal structure and be a little more hierarchical in thinking rather than just always operating 100% from particular moments of decision within the possible stories he or she is trying to tell. this tertiary i know for me is significant, but as an infj, it's not for the big goal structure as much as it is for how to connect that goal structure to where i'm actually at right now, to revise the goal structure with the given constraints of the possible stories i can tell from where i currently am.