Concentration and memory are ruled by Moon, so whenever your Moon is influenced by Pisces there is a chance you’ll have problems with concentration if you don’t use Pisces energy when you perform other Moon’s functions – eat, sleep, relax. But it’s also important to look at Mercury because it’s connected with the mind and how it operates. Here is an interesting case:
Reddit case: I’ve always suffered with concentration/memory issues, slow learning and brain fog
