Try to keep in mind that what you’re drawing, while relatively flat, still exists in a three-dimensional plane, and should still have form; and the way light and shadow are drawn should express said form. (Unless you’re purposefully making it to be more of an ‘icon’ or ‘symbol’ than an actual sword, in which case I would suggest simplifying it more).

A good way to practice this is to try drawing cubes, cylinders, and pyramids from different angles and perspectives with different light sources. Imagine your holding a cube at an angle to a very bright lamp. What parts of the cube would be dark? What part would the lightest? Is one side all completely dark, or does it fade out?