Is it just me?

So I've been making an effort to be more positive about things because no one wants to be around a Negative Nancy....
That being said, no matter how hard I try to break my habit of waiting for the other shoe to drop, I can't. I mean things could be going great in my life, but I never allow myself to really enjoy it because I'm afraid that if I do, things will make a turn for the worse.
Maybe if things didn't always tend to go awry I would get out of this habit, but so far my luck hasn't changed.
For instance, a few months ago I was thinking that my car was running great...the next thing I know, it breaks down and costs nearly $500 to repair.
Or if I haven't had an argument with a friend in a while and I start to think that we're good, we'll get in a huge argument and stop talking for a month or so.
I don't know if this is just me thinking negatively or if its just a defense making mechanism. Maybe I'm afraid of being happy as ridiculous as that sounds. Maybe things keep going poorly because I expect them to.
I don't know, maybe everyone thinks like this - or maybe it's just me...