My rescue Rottie is six and we've had her for 18 months. When we first got her I took her to classes and she did pretty well, but then we moved and I haven't found any round here yet. She is good a basic sit / stay / paw commands, can look at a treat or food until told to eat it, but she's a devil at coming back if there's something more interesting and does have a tendency to pull. She's much better with DH but when I'm walking her on my own she really pushes her luck (which is doubly annoying as I was always the one who took her to training!).
I'm pregnant with our first and I can't afford for her to pull while I'm pushing a pram, so we decided to start using a Halti. It's brilliant in that she never, ever pulls while wearing it, but she hates it. We give her treats / ball with it and she's better at letting us put it on (although we do still have to chase her head round a bit!) but every time I take it off she goes utterly mental.
She is currently curled up on her bed feeling sorry for herself, covered in mud and gravel and with a bleeding, grazed nose because she wouldn't stop rolling over and over the second I took it off. I managed to get her inside by putting my hand on her side while she was writhing around and talking very calmly to her, but it has really upset me and I feel like the worst owner in the world! Poor thing has got herself into a complete state 
Any ideas how I can remedy this? She does it a lot but this is the worst time!