antioptimist
skeptimist
uncheery
negaholic
gloomy
negative Nancy
negativist
bliss ninny
unsanguine
gloomy Gus
antioptionist
starry-eyed
meh
Eeyore
doom and gloom
cool
discourager
disappointment
disquietful
shoot
miserabilist
nonaccepter
ambivalent
afraid
despairer
cynic
take a dim view of
rejective
crybaby
wimp
chicken
discourage
negative
nonthinker
disillusionizer
that dog don't run
antipragmatist
gack
skeptic
doom-and-gloomer
antiskepticism
sceptic
unoptimistically
antiskeptic
nonsense
take the wind out of someone's sails
doubter
lukewarmist
againster
prisoner of hope