Read it some years ago, by a 'good' author name began with M maybe. Woman retires and is given a diary as a leaving present which scuppers her plans to kill herself. Then she starts filling it and making herself do what she has written?
OOOh thank you - I don't think its the golden notebook, because my mum was with me when I was thinking out loud and she mentioned that in a 'its not this' way! Someone 'good' like Muriel Sparks or Doris Lessing though. Dizzy - think! think!