An Emotional Character
Despite his reputation for being reserved, Stewart was quite emotional, especially regarding his work. According to his friends, he would really get into his roles. Maybe Jimmy Stewart was one of the first actors to really give method acting a go.

Kim Novak, who acted alongside him in Vertigo, revealed that after filming intense scenes, Stewart would stay in character even after the cameras stopped rolling. It could take him some time to snap out of it and return to his usual self.