Acorn was a loner before Eostra and Thunder asked him to join their new pack. Though he wasn't really enchanted by that at first, he found his place in the Winterfell Pack by becoming their first herbalist because of his knowledge of the plants.
Acorn know he his the best and that all the pack would be nothing without him saving their lives. He loves having his own den as well, where nobody bothers him for anything else than his work.