May refusing a request for a donation be conceived as ‘tempting fate’? Do people feel more vulnerable when they do not comply with such a request? In this paper we examine the link between subjective perceptions of vulnerability and people's willingness to help address a threatening cause. Results of five studies, examining a real life situation, hypothetical scenarios and a controlled lab game with actual monetary costs and rewards, show first, that deliberately helping is positively correlated with the perceived likelihood of becoming a victim of the same misfortune. Second, we show that refusing to donate to a threatening misfortune increases sense of vulnerability. Both phenomena occur especially for people with strong belief in a just world, who believe in a causal relationship between people's behavior and their fortune (rewards and punishments).