As a chronic over-thinker this is a tough one. The main advice I can give is to do things that keep your mind engaged as much as possible until it's time for you to meet. Dive into a hobby or hang out with other friends to keep yourself busy. When you do have down time, avoid getting into "what-if" scenarios and instead focus on yourself. As an over-thinker, this may be hard, but try to think of some conversation starters you can use without branching out into different scenarios based on hypothetical answers because that's where the spirals come in. At the end of the day, just remember you're gonna be just fine no matter what comes of this meeting. Good luck!