Bad luck can accompany excellent decisions without invalidating them.

A careful decision can still end badly, and it remains a careful decision. You choose under uncertainty with incomplete information, and sometimes the low-probability branch is the one that arrives. Treating every bad result as proof of a mistake teaches you to be timid rather than wise, and to abandon good methods for superstitions.

After something goes wrong, ask separately whether the reasoning was sound and whether the outcome was bad. When the reasoning holds, keep it. Let the grief be about the loss itself, not about a failure of yours that never happened.