If something is indelible, you better hope you never regret it, like the indelible tattoo of the name of your favorite band or the indelible first impression it might give people you meet years from now, especially if your taste in music changes.
The adjective indelible describes something that can't be erased or removed, like marks made by an indelible marker, or an indelible moment you will never forget, like your first day of kindergarten or the first time you visit a new, exotic place. It comes from the Latin word indelebilis, meaning "not able to be destroyed."