All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no doubt that Allah, The Exalted, is over all things Competent and that the hearts are in His Hand; He turns them as He wills. He is able to change the feelings in your heart towards your suitor. As long as this suitor turned away from you, you should strive hard to forget him, and perhaps Allah, The Exalted, has spared you from an evil by ending this engagement. So delegate all your affairs to Allah, The Exalted, Who Says (what means): {But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah Knows, while you know not.} [Quran 2:216] For more benefit, please refer to Fatwa 84544 about the cure for lovesickness.
Regarding Istikhaarah, we would like to point out that it is not necessary that a person would feel comfort in his heart or unease or the like after performing the Istikhaarah prayer. The result of the Istikhaarah prayer manifests in having one’s affairs facilitated for him or not, and either case is good for him. In essence, the Istikhaarah prayer is performed to ask Allah, The Exalted, to choose for His Slave what is best for him, as it is clear from the wording of the supplication. For more benefit on Istikhaarah prayer, please refer to Fatwa 173969.
Allah Knows best.