Remind yourself of what a positive, healthy step it is that you're taking. You're facing a situation that frightens you, but you've succeeded recently, and you can do it again. I like the idea of "anticipatory pleasure" too: think about how much better you'll feel knowing that you've got an expert on your side to help you get back on a more even keel. Also think about how good it will feel to tell your friend and all of us that you took that first step outside the door, and then another, and so on.
You can succeed, because you've already proved that with the driver's license trip. Next week's trip is that much closer to feeling more like you truly want to feel.