Royce 1970 has a a good attitude toward finding an error in one phase, then backtracking one step to fix it.
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Moving backward seems just as natural as moving forward. In Royce's words, such changes as “scoped down to manageable limits.”
This is in contrast to many old-style methodologists' attitude of moral condemnation toward people who backtrack. They're considered careless, or stupid, or undertrained, or not behaving professionally.
I offer the Fish Ladder Analogy.