The phrase "excessive pessimism" refers to a mindset or attitude characterized by an extremely negative outlook on things. It means consistently thinking that the worst possible outcome will happen, even when it may not be likely. Full definition
«Investors will be cautious on excessive enthusiasm in a similar vein to excessive pessimism in recent escalation of tensions.» (cnbc.com)
Unlike many «realists,» however, he keeps a vision of eschatological peace that guards against excessive pessimism about what is historically attainable. (religion-online.org)
I think many on this website need to overcome excessive pessimism and avoid high blood pressure. (justarsenal.com)