Who says? It seems to me that a lot of what you've posted, here and elsewhere, has been about sorting out what you should be doing and feeling and saying. Who you are and what's actually so for you often seems to get lost in the shuffle.
You obviously have more than one urge, is all! You've long had the urge to go through McLean's program and benefit from it. When McLean seemed to be giving you a hard time you felt frustrated and had the urge to settle for Riggs. Now that your trip to McLean is getting close, you have the urge to flee -- and, if I may point out, the urge to fight your urge to flee.

I suspect what you'd get the most from would be just continuing to get ready for your trip, taking a step back from the action, and watching your various urges fight it out. That doesn't mean you're doomed to go with whichever urge "wins". If and when that even happened, you might discover still other urges you didn't even know were there. Anyway, it'll always be your choice what to actually go with -- something that, for all I know, the McLean program might be about teaching you.

-- a.k.a., be here now*!

Today, for instance, you seem to be a day or two ahead of yourself -- your profile statement has you already at McLean.

Best of luck, jenna, and please do stay in touch!

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* Or, as another PC friend and I keep reminding each other: just keep swimming.