it's not you, it's me

Etymology
Originally used in American sports as a humblebrag consolation to less successful players. Popularized in romantic contexts by the 1988 American comedy 

Phrase

 * 1)  Don't blame yourself for the end of our relationship.

Usage notes
This cliché is used at the end of a relationship (usually romantic) with the intent of removing anguish and forestalling futile offers of improvement by the other person. Given that the other person has been judged to be an inadequate partner, it is usually understood as ironic but palliative. Given its impersonality and implicit dishonesty, however, it may be taken as patronizing or insulting the intelligence of the other person.

Translations

 * Catalan: no ets tu, sóc jo
 * Persian: به خاطر تو نیست، تقصیر خودمه
 * Portuguese: não é você, sou eu
 * Spanish: no eres tú, soy yo