If you are working traditionally, use a large mirror. Set it up as part of your work space and periodically hold up your drawing to the mirror, and look into the reflection.
No mirror? Use your cellphone. You can take a picture of your traditional art on your phone, and use the phone’s picture app to flip the image across the horizontal axis.
Flip-horizontal is one of the most powerful tools immediately available to any artist, and the earlier you find yourself in your art journey the more use you will get out of it. Try it a few times and I think you will be convinced.