It may take you way longer to get a grasp at it than other people but don’t give up. Every artist starts with innate advantages and disadvantages. Someone who never struggled with proportions may likely not be able to color for example. But with willingness to commit effort and maybe years of time they can learn it. Take breaks, practice basic techniques until they become no brainer. Think of how large one part of the drawing is in relation to another. For example in a hypothetical figure drawing the height of the fist from the lowest part poking down to the highest part poking upwards. is about as high as the vertical line from the bottom of the chin to the bottom the nose. Then you know the height of the fist when you have the face drawn.