The question can be transtlated as "my hands wouldn't follow my eyes but the image in my brain". To solve this problem, you can start with a two step training which I found useful for myself:
Step one: Draw some "C" or "S" lines as you like, make them cross randomly. Make sure it's not too complicated. Then get a new piece of paper and try to "duplicate" the shape. Keep doing this until it looks 95% alike the random shape.
Tips: You can simplify the shape as points and polygons with certain angles, make sure to measure everything with your eyes only. This will force your brain to focus on the shape and measure everything more accurate.
Step two: Instead of draw a whole body figure, try start with parts of bodies. Find realistic photos and do it as step one. Your brain will gradually used to the real propotion rather than the manga style.
It takes time to retrain your brain and hands, but I have faith on you~Good luck~
