I know a couple of people IRL who never seem to have a positive reaction to anything. The proverbial "every silver lining has a cloud" people: got a raise? just means more taxes. Sunny day? skin cancer. Cloudy day? cold and mud.

For the particular people I know, it seems like a self-esteem thing - like they don't feel themselves worthy of happiness, so they have to preemptively destroy anything positive. Or maybe just be contrarian to prove they're smarter than everyone else. It's exhausting.