Make a log of how many times you get positive or negative luck. I am pretty sure it is about equal, we just tend to notice the worse things more often. For example, there is a "test taking tip" to not second guess your answer, as you will likely change it to the wrong response. Statistically that is not true, its just that we notice more often when this happens because we see a big fat X or 0 next to the incorrect response.
I've heard some interesting theories about negative luck though, some say Premium users experience it more often for the sake of balance, lol