On the other hand the two things compared may be so far apart that we fail to see the point. The trick is to be original and true to experience. One can say anything is like anything. There are no two things in the world, said Cicero, that cannot be compared. When a writer is using an A is like B formula to make a comparison and either element distorts the other, or contradicts the other, he might haveforced a mixed metaphor.
Mixed metaphors are like double exposures in photography.
Some may be deliberate, some may be accidentally good. Most are plain failures, with comic results, ugly or blurred. Images are not felt as mixed when the poet makes a clean break with one before going on to another.