Agile Development community, we use the term “technical debt” to refer to this problem.  When you don’t keep your code clean, you incur debt, and as in other areas of life debt reduces your options – it can become crippling over time...

Michael Feathers compares technical debt to credit card debt. I think it's very apt.

Maybe I should try to read his _Working Effectively with Legacy Code_ book another shot. I felt it was too beginner for me. I should just read it. You can always get something new from rereading the basics.