"Man does not tire of praying for good," meaning: he does not become bored. "But if evil touches him, then he is despairing, hopeless." To the polytheist, the good is the worldly life, health within it, and prosperity. "And if evil touches him," in the form of loss of wealth or an unexpected illness, he does not hope for reward in the Hereafter, nor does he hope to return to the prosperity he was previously in.