Having a plan B for things is a bit silly sometimes. If you need to parse some data, your plan A is to write a parser, and your plan B is...to write a parser in a slightly different way? Pair program as you write the parser? That's not really plan B, it's just redoing plan A if you mess up.

Plan Bs make sense for external dependencies, but for internal work they imply your current solution has feasible alternatives, which is often nonsensical.