Its hard to explain whats so moving about them. When she describes some lazy afternoon, she just gets it so right that all the vast range of human experience seems to be contained in this afternoon (whereas in any Great American Novel-esque tomes you read only a fraction of that experience is ever expressed). But at the same time, it was just this cute little vignette that had very satisfying descriptions of flowers and little girls playing. The journal will help you understand her sadness as its expressed in her work.
You know when you are very, very upset, and you see something so beautiful or even funny, youre likely to become on the verge of tears? Thats how Mansfield sounds in her stories - the stories are that beautiful thing that she sees.
She is most often compared to Chekhov, and its not difficult to see why. I truly believe that Mansfield innovated and practically invented the English (language) short story.