good damage comes from popular show [bojack horseman]. the phrase means damage that helps or contributes to yourself in a positive way. the opposite is bad damage, which only serves to make you an angry, [regretful] person. plain damage fits in there too. plain damage is just the type of trauma and hurt that just stays there, doing virtually nothing. you remember, it hurts, but it doesnt make you better or worse. kind of like how the [meteor] that killed the dinosaurs leaves damage on the earth, but the damage changes little to nothing about the area.