Another term for a literary technique is literary device. Literary devices are any methods an author might use to tell the story or illustrate a point. Common literary devices are narrative techniques, plot devices, symbolism, recurring motifs, and any language devices, such as figurative language and repetition. Shakespeare certainly makes use of many different devices throughout all of his plays depending on what he wants to convey. In particular, in Twelfth Night, one thing Shakespeare conveys about love is that it can be very cruel and painful. We can see devices he uses to portray love as cruel and painful in the very first scene. Specifically, Shakespeare uses apostrophe to personify love as cruel.
Apostrophe is a certain type of personification in which some abstract idea is not only personified but also addressed as if it was a person that was physically present. Dr. Wheeler gives us an example from John Donne, "Oh, Death, be not proud" ("Literary Terms and Definitions"). Since here, Donne is addressing death and commanding it to not be proud, which is a human emotion an abstract idea cannot feel, we see that this is a perfect example of apostrophe. In the opening scene of Twelfth Night, Duke Orsino uses apostrophe to address love and point out its cruel nature, as we see in the lines:
O spirit of love! how quick and fresh art thou,
That, notwithstandng thy capacity
Receiveth as the sea, nought enters there,
Of what validity and pitch soe'er,
But falls into abatement and low price. (I.i.9-13)
Not only are these lines addressing love like a person, the lines are also metaphorically likening love to the sea. Just like the stormy, turbulent sea swallows up ships and everything in ships, love also swallows up human emotions. In addition, when anything like a ship drowns in the ocean, it "falls into abatement and low price," meaning it becomes worthless. So, if a person falls in love just like one might fall into the sea, that person also becomes destroyed and thus worthless. Since Orsino is arguing here that love makes things worthless, we can also see that he is calling love a cruel and painful emotion.