If you want to know if you are having an epic dream you will know by how aware you are of your dream. If you are very aware of your dream, then it is possibly an epic dream. Another way to tell if your dream is epic is if you can see your life from a different perspective once you have had a dream and if the dream gives you emotions that you are not used to.
An epic dream can happen if it is very vivid and if you can remember the dreams easily because the images are so strong that you cannot really stop thinking about them.
If the dream makes you feel shocked and excited when you wake up, chances are you are having an epic dream. When a dream lasts for years and years in your mind, the dream is probably an epic dream.