We learn from A Midsummer Night's Dream that love is a form of madness. It may be many things, but rational it is not. Shakespeare, in this madcap frolic through love's landscape, offers many examples of the way love doesn't make sense.
Hermia, for example, refuses to marry Demetrius, even though he would be the rational choice. Demetrius was chosen for her by her father, and the law backs his right to pick his daughter's husband. As her father points out, there's nothing wrong Demetrius. Nevertheless, Hermia, in love with Lysander, instead flees to elope with her beloved.
Likewise, Titiania, a fairy queen, falls in love with the lowly Bottom, even though he has an ass's head. This is attributed to fairy magic, but what is the world of fairies and magic other than a world of fantasy and irrationality? (Even the play questions its reality.) Titiana, in her affection for Bottom, illustrates that love is blind and more than a little crazy.
Helena shows love's irrationality in her mad pursuit of Demetrius. This reveals the darker side of love's madness: she is willing to put up with abuse to be with her beloved.
Puck is only too accurate when he states, about humans and love: "Lord, what fools these mortals be." But humans would not want it any other way.