Our brains are wired to see patterns that prove ourselves correct. It's evolutionary, something hard-wired in each of us. If a person approaches anything/anyone through a negative lens, believing everyone is out to get them, he/she will find evidence to support that, while his/her brain passes over evidence of the opposite.
By entering life from a jaded or negative space, one's experience is more likely to meet that expectation (or lack thereof). If we approach life expecting a person to be boring or superficial or angry, then we will see the other person through a filter, looking for evidence to of these qualities. We create our own reality this way.
So how can we change this paradigm?
The answer's simple, but not necessarily easy. Enter the experience with an open mind and heart. Try to clear your mind of expectations and beliefs about what something is or is not before you try it. No, I'm not encouraging a Pollyanic, naive approach. But you can begin the process of looking towards life with a fundamental belief in place that will anchor you: you already have everything you need inside of yourself. This will allow you to remain as neutral as possible. At the same time, it will also allow other people to show up freely as himself or herself, without the filtering effect of your judgments and assumptions.
That said, if you find your judgements bubbling up, simply to notice what your mind wants to label "bad." The beauty of being aware in this way is that you can take your power back, and no longer have to navigate dating from a negative space.
Look at this way: the world is so much larger and more spacious than the worlds each of us inhabits each day. Appreciate that space, and realize how freeing it is. There are beautiful, open, conscious individuals everywhere.