lets bygones be bygones

Verb

let bygones be bygones (third-person singular simple present lets bygones be bygones, present participle letting bygones be bygones, simple past and past participle let bygones be bygones)

1. (idiomatic, intransitive) To disregard or ignore a past difficulty in a relationship or an offence (when dealing with another individual).
   • "Never mind, I'll give you a hundred dollars for it," said the king; "you did me out of horse and saddle the other day, and the bridle too, but I'll let bygones be bygones, if I get the pot."1881, P. Chr. Asbjörnsen [i.e., Peter Christen Asbjørnsen], “Peik”, in H. L. Brækstad, transl., Round the Yule Log. Norwegian Folk and Fairy Tales, London: Sampson Low, Marston, Searle, & Rivington...

   Synonyms:

   forgive and forget