Calluses, those areas of crusty thickened skin on your hands and feet, are part armor and part liability. Gymnasts obsess about shaving them down; runners worry about keeping them built up. With some smart management, it’s possible to have happy, tough skin that doesn’t give you problems.
Scott Kelly has said that in space, because he didn’t need to wear shoes for a whole year, the bottom of his feet became “baby soft”. But because he used the tops of his feet to hole himself onto railings, he developed thick calluses on tops of his feet! How weird is that?