The theme of stubbornness could be prominent. Just like the saying 'old habits die hard', characters in the story might be extremely stubborn in holding on to their old ways. It could also be about the passage of time and how long - held habits are formed over time and are difficult to let go of as time progresses. For instance, a person who grew up in a certain era with specific values and habits related to that time may find it hard to adapt to new values in a different era.
One possible theme is the power of routine. People get so used to doing things a certain way that it becomes almost second nature, and changing that can be a huge struggle. Another theme could be self - improvement and the barriers to it. If someone wants to better themselves but is held back by old habits, it creates an interesting conflict.