Mankind are tolerant of the praises of others as long as each hearer thinks that he can do as well or nearly as well himself, but, when the speaker rises above him, jealousy is aroused and he begins to be incredulous.
ThucydidesFor if many ill-conceived plans have succeeded through the still greater lack of judgment of an opponent, many more, apparently well laid, have on the contrary ended in disgrace. The confidence with which we form our schemes is never completely justified in their execution; speculation is carried on in safety, but, when it comes to action, fear causes failure.
Thucydides