Examine your guess. Your guess may be right, but it is foolish to accept a vivid guess as a proven truth — as primitive people often do. Your guess may be wrong. But it is also foolish to disregard a vivid guess altogether — as pedantic people sometimes do. Guesses of a certain kind deserve to be examined and taken seriously: those which occur to us after we have attentively considered and really understood a problem in which we are genuinely interested. Such guesses usually contain at least a fragment of the truth although, of course, they very seldom show the whole truth. Yet there is a chance to extract the whole truth if we examine such a guess appropriately.
Many a guess has turned out to be wrong but nevertheless useful in leading to a better one.
No idea is really bad, unless we are uncritical. What is really bad is to have no idea at all.