At risk of coming across like Jaden Smith, let me wax philosophical about programming.
All code is thought, and development is unfolding of a thought process using the computer as external infrastructure in which to hang thoughts that don't all concurrently fit in your head. Therefore, the current state of your code reflects your current understanding of the problem you're solving. This understanding has to improve over time, but it usually does not radically change. Being good at development means being good at expressing your current state of mind in code; writing it so it's a true reflection of your thinking, rather than a muddled one.
Therefore, when you write code in a way that it's in harmony with your thought, changing your thought in a small way will produce a similarly small change in code. If changing your thought in a minor way causes large changes in code, it means you're expressing yourself poorly.