I was such an optimistic person, but then there was all of these negatives floating around in my mind all the time, that I just didn't have that same bubbliness that is core to my personality.

我是一个非常乐观的人，但是所有这些负面因素一直在我的脑海中萦绕，以至于我没有像我的性格核心那样的活泼。