It is a bad plan that admits of no modification.

A plan that cannot bend will break when conditions change, and conditions always change. Rigidity usually comes from having tied your pride to the original version, so that adjusting it feels like admitting you were wrong rather than like steering. Good plans have joints in them.

With whatever you are currently committed to, name in advance the things that would make you change course. Decide now what evidence would count. That way the adjustment, when it comes, is a piece of the plan rather than a defeat.