cheating

Just read a manhwa about cheating so I’ve got a question, did someone close to you cheat on their partner? or did you ever have a partner that cheated on you? How did it feel? Like I know, it's painful but I kinda wanna know more about it. I'm especially curious about the former, like I've seen posts talking about the latter, like how they feel rage, sadness all those stuff but I don't think I've seen one go into detail about the former. Like, let's say, your bestfriend cheated on their partner or your father cheated on your mother, idk