Since you are dreaming that you are forgetting something, you might explore its opposite meaning. Perhaps you are overly focused on something that some aspect of your higher mind finds trivial. On the other hand, you may be dreaming of what you are forgetting as a way of bringing it into a higher level of focus. Like dreams where you seem to be Awake, while actually asleep, dreams of forgetting show your Anxiety about having so much on your plate that you fail to ‘remember’ the important things. The symbolism surrounding what you are forgetting will provide additional insight into what it is.