Somewhere in between.
I have a natural tendency to pessimism that I am aware of and have to fight against, or it would drive my thinking all the time. I try to have a more balanced outlook and use my sense of humour where I can to keep a sense of proportion.
When I go low, I get very pessimistic and in the past, suicidally so, but at least now, I have insight into why I think that way and I just try and ride it till it lifts.
Which it always does....