我记性不好别跟我谈曾经
[wŏ jì xìng bù hăo bié gēn wŏ tán céng jīng]
It means 'Don't talk to me about the past because I have a poor memory'. This could imply either forgetfulness in the true sense or intentionally forgetting painful or unnecessary past events. In short, the person might prefer not being reminded of previous happenings.