timo Just scale it down to 36x36 (or whatever the smalles size on mobile is) and you'll see what from the little details are still visible/left.
Please simplify the icon! There are too many informations tried to include/consider! And if you can't make it better, abstract your idea of a Diary and create a UNIQUE icon.
There is a serious reason why all the big, successful apps have just one easily recognizable icon.