Never Enough

Why do I have such a hard time enjoying something good happening?

Backstory that you've probably already heard:
I used to work on campus at UCSB in the main kitchen and the entire time I worked there, I had a mad crush on one of the chefs, Ricardo. We were friends and hung out a few times, but nothing ever came of it and we fell out of touch after I graduated.
Flash forward seven months to the Gunther concert, where I ran into him on campus. We chatted and did our How've-You-Beens and then he had to go. No big deal. Another few months go by and then one day out of the blue he called me up and asked me if I'd like to have dinner and see a movie. A month of schedule juggling later, we finally went out. And we still are.
It's all very Sixteen Candles.
So here's my deal. I keep thinking that it's a set up or something. I don't know how to explain myself completely. I just keep anticipating everything to crash and burn. Which I am well aware is Crazy Talk. But it's in my head and I can't get it out. It is seriously starting to bother me. He does these great and unexpected things, and I can never just relax and fully appreciate it. I mean, he knew I liked wine, so the other night when he came over to watch a movie, he brought a Riesling for christsake. Not to mention the fact that he loved Serenity.
So what is my problem? Why do I always have this vague sense of dread whenever something good is happening in my life?