knowing when to stop

I think I'm stopping on this one before I overwork it.  I don't think it's all the way there yet, but I'm afraid it's going to get murky if I darken the face any. So...I started this...

Still a lot to do, this is just the first few layers.  I'm going to try and not overwork this one, so I have to remember to have a light hand and think before I paint.  I'm use to oils where I can layer and layer and layer, and cover up.  Not so with watercolors!  I'm learning...