the point of dream journals is to help you get better at dream recall. even if you down' remember anything, write down some sort of emotion you may have felt or just how you slept and if you used any techniques and your results. the more you do this in time the more dreams youll be able to recall. i think you should just stick with it for a little bit. I have some nights where i don't remember thing, its frustrating but its also cuz i work night shifts so my sleep schedule is out of whack.