MattVogt,
Wow, thank you for all of the nice things you’ve said about the Anatomy Forum! This is highly encouraging, and it is really amazing to get this kind of feedback! Thank you. 
I think that with resect to your drawing, you need to relax your lines a bit, and slightly loosen up. I know this is easier said than done, particularly in the beginning. What I always recommend is to TRACE your initial drawing, either traditionally or digitally ~ this affords you the ability to see mistakes more clearly, and it takes one away from the mentality of having to get everything right in one go. Once you have traced your image, then redraw, freehand, the same image again. I think that this will really help! 
Thanks also for showing us your shading exercise.
I think you might try blending a bit more, and what I would recommend is to blend not using the smudge or blur tools, but practice using varying opacities of lighter and darker values to get things to work. This will train your eye to see values more clearly. You can sample a value with the eyedropper, and then go either slightly darker or slightly lighter, and paint values with varying degrees of opacity. I think using this technique will help you to see values to a greater degree. 
zhuzhu,
This is not a bad sketch! Traditional watercolors are nearly impossible to correct. You might try doing a more complete pencil sketch first (lightly) before coloring with watercolor. 
DreamMaster,
Lol, looks can be deceptive!
Be careful not to scrunch the arms and head too low close to the body ~ right now her torso looks pretty good, but her head and arms seem to be too short proportionally ~ I would raise the head a bit, and adjust the arms accordingly.
Additionally I would suggest starting to blend using the technique I described above ~ sampling tones, and going either slightly lighter or darker, and painting with various opacities over your existing work.
Finally I would recommend adding a darker ground beneath the figure so that the figure does not appear to ‘float’ in space.
Good work so far, and just continue to push those values and to refine your drawing! 
Cheers! 
~Rebeccak