This subjection to a possible self, a self not to be absolutely predicted about, caused her some astonishment and terror; her favorite key of life--doing as she liked--seemed to fail her, and she could not foresee what at a given moment she might like to do. 
This powerlessness to predict her own behaviour caused her some astonishment and terror; her favourite idea of doing as she liked seemed to fail her, and she could not foresee what she might choose to do. 