Failure should update your method before it updates your belief in yourself.

The first thing to change after a failure should be the method, not your assessment of your own worth. Method is what actually produced the outcome and what you can actually revise. Rewriting your self-belief instead leaves the faulty process intact and adds a second problem.

When something fails, go straight to what you did and how, in detail. Fix something there. Save any conclusions about your capability for much later, if ever.