Charles Dickens said “There are dark shadows on the earth, but its lights are stronger in the contrast.”
This is what I found on Wikipedia about Contrast in literature, by the way very interesting:
Contrast is the antonym of simile. In poetic compositions, it is common for poets to set out an elaborate contrast or elaborate simile as the argument. In Renaissance poetry, and particularly in sonnets, the contrast was similarly used as a poetic argument. In such verse, the entire poem argues that two seemingly alike or identical items are, in fact, quite separate and paradoxically different. These may take the form of ‘my love is unlike all other women’ or ‘I am unlike her other loves.’
If you are interested in using, or practicing, contrast in your poetry, you might like to read this article “Contrast as a Method of Developing Poetry”. At the end of it you will find an exercise. Enjoy!