noun

a person who expects or is excessively ready to accept failure.

pessimist,fatalist,yielder,cynic,prophet of doom,doomwatcher,misery,killjoy,worrier,Job’s comforter,quitter,doom and gloom merchant,doomster,wet blanket

adjective

demonstrating expectation or acceptance of failure.

we have a duty not to be so defeatist

pessimistic,fatalistic,negative,resigned,cynical,discouraged,despondent,despairing,hopeless,bleak,gloomy,gloom-ridden,looking on the dark/black side