I need help with overthinking!!!!

I need advice on why I may be over thinking about being with someone I've liked for many, many years. Here's a bit of backstory, I will call the guy I like "Jay" in this situation. Jay used to be my brother's best friend, they kind of still are but not as close as him and I are currently or have been since we started talking. I have known him since high school and we always were on and off about our situation/ friendship for the past 7+ years due to us finding other relationships, distance, work and/or school, the list goes on. He got married a few years ago and now he's finalizing a divorce and he reached back out to me, and after taking for a month or so we planned to finally go out of town and go on an official date for the weekend and try to be with each other but not rush into anything. I made it clear we don't have to rush into anything since he is recently divorced, and I haven't dated for almost 3 years because I never thought I was good enough to be in a relationship with or it never worked out. But with him, he has made it known he cares for me, as well as likes me very much and if it turned into something more, he wouldn't be opposed to it and then we'd be together but if not, that is fine too we will remain friends. But with this date coming up this weekend, I can't help but be in my head, just overthinking the situation and running all the things that could go wrong in my head, and I feel scared to even go see him now and I'm not sure why this is happening. I am just assuming things are not going to work out due to my past before anything has even begun, How do I get through it or get out of my own head, thinking things aren't going to work out from the jump? Why do I feel so anxious or scared to finally go out with him?