I am not a pessimist. I am paranoid. My major jobs have required paranoia.
I ran and helped maintain a large Van de Graaf generator. It had high voltages all over the place. Bad things could happen if those voltages got loose. The machine even gave me electric shocks when I wasn't careful to keep me alert.
And then I joined the museum world. Let me put it straight: entropy is out to get your stuff. Your job is to find all the ways entropy can get in, and block them.
As for the glass being half full, or half empty? Forget it. The glass is twice as large as it needs to be to handle the drink.