There are many articles about this topic, I just picked the first one I found on google, even though it's about dobermans, it applies to all puppies.
Puppy | Dog Breed | Pet Supply at Doberman.org
Read the Second Fear Imprint Period paragraph. If jokingly hitting your husband is something you do a lot, then you need to use the advice given to desensitize her to it or she will always be afraid of it. Or just don't horse around with him during her fear imprint period because it may cause her to be permanently scared of that. There are many other articles you can read about it as well, I just picked a random one.