Always afraid something bad is going to happen.

Brené Brown talks about what you're describing extensively in her TED talk "The Price of Invulnerability." It's called foreboding joy, and it's essentially a numbing function. By taking situations and, essentially, preparing ourselves in advance for any sort of difficulty that could arise, we're attempting (unconsciously) to anticipate and minimize the discomfort or grief or other unpleasant feeling that might happen. And it really sucks because when we forebode joy by trying to minimize fear or grief, we also prevent ourselves from being able to experience joy.

Most of the time, we do that because we've had a lot of disappointment, so it's a learned behavior to make it hurt less. Things like "Oh, I'd like to get this new job, but I won't be really upset if I don't", or "Well, i met this guy and he's really cute and I'm hopeful, but if it doesn't work out, that's OK" keep us from feeling genuine excitement and anticipation, and from experiencing the joy full on... and, while they succeed in numbing the pain, it comes at a very high cost.

Then, when you add foreboding joy to the biochemical interactions that are going on with OCD, you have a situation is even more amplified. There's an excellent book called "Brain Lock" by Jonathan Schawartz MD, who has been researching and focusing on OCD for many years. His approach is mostly cognitive, but has shown remarkable effect... and as a byproduct of practicing his techniques for OCD, you can also use them to work on letting yourself be more vulnerable (open) to true feelings.

Generally, when you're dealing with a combination of foreboding joy and OCD, simply trying to tell yourself that things are unlikely will probably not be a very effective strategy, because of the mechanism/reason why the foreboding is happening in the first place.

Separate from Schwartz' OCD strategy, the strategy that generally works the best in dealing with the OCD, according to the research, is to identify the places and circumstances where you are most likely to come up with the foreboding thoughts, and simply recognize that what you are doing is a foreboding behavior, and then make the conscious choice to change how you are experiencing the situation in that moment; for example (using the scenarios I described above), by allowing yourself to get excited about the possibility of having the job, imagining what it would feel like to have it, and so forth. The downside is that it won't numb the negative feelings if you don't get the job, but that's a part of being human and living in the world. The upside is that you will be able to live more fully and be more emotionally available to yourself and others around you... and, as a byproduct, it will likely reduce some of the symptoms of the OCD as well, particularly if you combine it with the exercises in Brain Lock.

This is a very solvable problem.