He might be initially heartbroken. Harry has always been a bit of an emotional person, so he could go into a state of depression for a while. He might isolate himself from his friends and focus only on his studies or fighting against the dark forces, using it as a way to distract himself from the pain of the rejection.
One reason could be that his mate has different life goals. Maybe she is more focused on her own magical career and doesn't see a relationship with Harry fitting into that at the moment. Another possibility is that there are misunderstandings between them. For example, Harry might have been too involved in some dangerous adventures and his mate thought he didn't value their relationship enough. Also, it could be due to external pressures, like her family or friends not approving of Harry for some reason.
He could also give his mate some space for a while. Sometimes, distance can make the heart grow fonder. By giving space, his mate might have time to think about their relationship and realize what they are missing.
It could also be due to differences in their personalities or goals. If Harry is very adventurous and his mate is more cautious, they might not see eye - to - eye on certain important matters. And this fundamental difference could lead to the mate rejecting Harry.
One possible reason could be a misunderstanding. Maybe his mate misinterprets something Harry does or says. For example, if Harry is often away on dangerous adventures, his mate might think he doesn't care about their relationship and reject him.
In some fanfictions, Draco might initially become withdrawn. He could isolate himself from others, brooding over the rejection. For example, he might stop participating in social events he used to enjoy.
It could be Hermione. In some alternate interpretations, there could be a situation where Hermione, while trying out a new and powerful magic, accidentally hurts Harry. Their friendship is put to the test as Harry has to deal with the pain and Hermione has to come to terms with what she's done.
Rejected mate fanfiction often involves a plot where one character in a fictional relationship, often in a supernatural or fantasy setting like werewolves or vampires, is rejected by their supposed mate. It can explore themes of heartbreak, growth, and sometimes redemption as the rejected character tries to find their place and may even change the mind of the one who rejected them.
Maybe it's Ron. Suppose Ron gets jealous of Harry's fame and power and, in a moment of weakness and envy, decides to abandon Harry to die. This would create a lot of drama as Ron and Harry have been friends for a long time, and such a betrayal would be a huge shock to the story's readers.