If a girl thinks I'm not worth liking back and is really mean about it I keep repeating to myself "She'll rather wear a sweater soaked in sour milk for a week in the summer rather than consider you a person." or "She'll sooner kneecap herself with hollow point rounds than suffer your presence for another minute" or "She won't feel peace until you encounter a lonely violent death in a place where no living being has walked in a thousand years." That really helps me resolve my regret for ever liking them in the first place. I wouldn't encourage anyone else to think like that though, there's no need to be a damaged empty husk like me.