Does the heart's failure to turn away from a suitor after his rejection following Istikhara prayer mean that the Istikhara prayer was not performed correctly?

The preponderant view is that after performing Istikhara (prayer for guidance), the supplicant proceeds with the matter and does not abandon it unless Allah diverts them from it. Based on this, since you have sought Allah's guidance through Istikhara, we hope your decision will be good. You should strive to turn your heart away from attachment to this man by not dwelling on intrusive thoughts and by occupying your time with beneficial activities.