Clean code always suffers when new feature comes in. So don't be lazy and try to put that new functionality into a new class instead of trying to squeeze it in

Clean code always suffers when new feature comes in. So don't be lazy and try to put that new functionality into a new class instead of trying to squeeze it into existing classes and functions - that makes it more testable, separated and uses the "composition instead of inheritance" dogma. It will make the code somewhat cleaner and a thousand time more refactorable.