Sharing the load
Clara, and most of the companions, have always gone along with the doctor on grand adventures and while they were usually contributors to the successful outcomes, when things were at the darkest they always expected him to pull a rabbit out of a hat to save everyone. It is almost always him that has to make a decision that impacts lives. Maybe as part of his cantankerous new personality the decisions of the past are weighing more heavily on him and he wanted to give her an idea of the load he carries....and that prancing around the universe isn't all just fun and games for him. This personality is older and might be a little bitter of the way the young tend to act as though nothing can hurt them then run to mom and dad when they skin their knees.
Just another perspective.