Opening the book…
A loss is the most expensive information you will get all year, and most people throw it away by explaining it as luck, conditions, or unfairness. The useful question is not whether they deserved it but what they perceived that you did not. Until you can articulate their read of the situation, you will lose the same way again.
After a loss, go back through the tape, the file, the pitch, the game — whatever record exists — and reconstruct their decisions in order. Write one paragraph in their voice explaining why each choice made sense. Ask them directly if you can; most people will tell you.
If the outcome genuinely turned on chance or a bad call, say so and move on rather than manufacturing a lesson. And don't study so long that you stop practising — set a limit and then get back to the work.