It was tough the first time I saw Jewel or Silva hang their heads and appear sad or confused when told no with a corrective tone. We're not talking yelling or bellowing either, it was almost as if the word and the tone broke their little hearts. We learned that a simple lightly spoken "uh ah" or "leave it" etc. worked best. Geez the first time I told Silva no I swore if she were human she would have cried, Jewel looked similar. I remember going back to them immediately and distracting them in some positive way like you would re-direct a 1 or 2 year old toddler.
RFD, we had a 5 year old boy we rescued, he was with us for seven years until he passed, his name was Thorn. He had lived primarily with sled dog folks most of his life. Not that I think he was mistreated but his ability to trust was almost nil. He was more used to being in harness than having a leash hooked to his collar and going for a walk. Well, he was a darned stump puller on a leash. lol Probably why he excelled in weight pull and also made a great wheel dog on our rec team. The first few times I tried to walk him, he put his head down, dug in and pulled soooo hard. It truly was like a tug of war and he was the winner. Any leash correction I gave and he became paralyzed. He just froze. Well that wasn't working. He was not especially food motivated either so it was a challenge to walk him. Walking him was never easy but it did improve as the years went by.
Life lesson for us: not all dogs of the same breed behave the same, and you definitely better factor in their previous environment(s) and history if you wished to have a successful positive relationship. It got so that any challenge that came along we would sit back and say "okay, what did we do wrong, what can we change to improve or eliminate this problem." That is truly the challenge I love about sharing my life with dogs.