likely/unlikely to lead to success
(un)propitious - (un)favourable
Something ‘propitious’ presents a favourable circumstance and makes it likely that something will turn out for the best. This formal word has an element of portending to it; as if there is a sign or strong 'gut instinct' that everything is pointing towards a happy outcome. 'Unpropitious' is the opposite; in other words, something that predicts or suggests a bad or unfavourable outcome. Most commonly encountered in written English.
I think losing my job will lead to a propitious outcome for me because now I can take my career in a whole new direction.
With everything under lockdown and the economy tanking, now is not a propitious time to be starting a new business.
I do intend to tell Sarah the bad news, but I want to wait until the most propitious moment first so that I can soften the blow.