Obviously I didn't get any picks while driving so I will add those from ground driving a few nights ago.
Of course we started out walking on the lunge line. This allows him to loosen up before asking much more of him. Since all we were doing is long line work, he is only wearing the harness saddle.
He has loosened up and is starting to overstep at the walk. After a few laps around like this is when I ask him to jog or trot. When he loosens up in the trot and there is a noticeable change in his gait, I will either let him stop or if he's feeling good, I will allow him to lope. 
He's sporting hs new boots... The blue string is baling twine holding the tugs to the saddle. This way if I ned to run the lines thu them, there isn't as much swing and the line stays close to his side. 
Now that he's in the lines, he tries to give me some grief. Because he's like that and he can. lol While his head is up and he's not on the bit or in the bridle (on or behind the verticle), he is finding his balance and driving up under himself from behind. He is gaping at the mouth in protest as I start asking him to bend. We are back to doing long line work wearing the snaffle- in the beginning we switched away from this because he was putting his tongue over the bit.
He has started to drive up under himself and lift his shoulders. not quite breaking over at the poll, yet, but he's getting there. 
And sometimes even when they are moving in balance, their head is up and their nose in front of the vertical. 
He's starting to reach out and extend and also soften his jaw and relax. 
Here he's in a nice woking trot. Soft in the bridle, relaxed and trucking along. 
We have stopped and changed direction, picking up the trot again. He is relaxed and forward again in a nice working trot. 
And he gets a little resistant again... fussing and trying to see what he can get away with, because he does this at times. Some horses and ponies do this all the time, where others try once or twice, give in and that's it. This is his way of expressing himself. My mare turns her head to the side and does this weird thing with her mouth. One of the things about working with horses is to recognize their subtleties. They all have these little ways of showing us they like or don't like something. We as their owners or trainers need to learn what they are and when they do it. It can prevent a big mess later on. 
And within a stride or two he softens, giving to the bit and going forward again. 
The head has come up a little again, but he's moving forward like he should. He's reaching up under himself and making use of the bell boots with the overreaching. He's such a handsome little bugger. 😁And since we started out talking abut driving, it's only right that the post finishes on that. We did some walking, trotting and also loping, both directions of course. Our upward transitions were easy to get and the downward transitions came just as easily. I have always told my Little Man, "Bring it down to the trot" and he does it so effortlessly. Then I tell him "Easy" and he slows the jog, "Bring it down to the walk" and Boom! He gives it to me with nothing further. A few soft whups and then whoooaaa and he shuts it Down. Most of the time I don't even get to the whoa because he has already shut it down. He knows it's coming next. 