A meaningful loss deserves a review.
You don't need to replay every conversation for the next three days. Go back through the opportunity while the details are still fresh and ask useful questions.
Was this opportunity properly qualified?
Did the prospect have a problem we could actually solve?
Was there a genuine reason for them to act?
Did I understand how the decision would be made?
Was I speaking with the people who could influence or approve the purchase?
Did I understand the competition?
Were the next steps clear throughout the process?
Did something change that I should have recognized earlier?
What would I do differently if the same opportunity appeared tomorrow?
Sometimes the review will expose a mistake.
Good. Now you have something you can improve.
Other times you'll go through the deal and realize you sold it reasonably well. The prospect still chose another option.
Some losses expose something you can improve. Others come from budget changes, internal politics, timing or decisions you couldn't control.
A useful review separates the two.
Fix what belongs to you without taking responsibility for everything that happened.